Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, 5 Dec 2019 11:49:00 +0530 Kirti Wankhede wrote: > On 12/5/2019 11:26 AM, Alex Williamson wrote: > > On Thu, 5 Dec 2019 11:12:23 +0530 > > Kirti Wankhede wrote: > > > >> On 12/5/2019 6:58 AM, Yan Zhao wrote: > >>> On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: > On Wed, 4 Dec 2019 23:40:25 +0530 > Kirti Wankhede wrote: > > > On 12/3/2019 11:34 PM, Alex Williamson wrote: > >> On Mon, 25 Nov 2019 19:57:39 -0500 > >> Yan Zhao wrote: > >> > >>> On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > On Fri, 15 Nov 2019 00:26:07 +0530 > Kirti Wankhede wrote: > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > >> On Thu, 14 Nov 2019 01:07:21 +0530 > >> Kirti Wankhede wrote: > >> > >>> On 11/13/2019 4:00 AM, Alex Williamson wrote: > On Tue, 12 Nov 2019 22:33:37 +0530 > Kirti Wankhede wrote: > > > All pages pinned by vendor driver through vfio_pin_pages API > > should be > > considered as dirty during migration. IOMMU container maintains > > a list of > > all such pinned pages. Added an ioctl defination to get bitmap > > of such > > definition > > > pinned pages for requested IO virtual address range. > > Additionally, all mapped pages are considered dirty when > physically > mapped through to an IOMMU, modulo we discussed devices opting > in to > per page pinning to indicate finer granularity with a TBD > mechanism to > figure out if any non-opt-in devices remain. > > >>> > >>> You mean, in case of device direct assignment (device pass > >>> through)? > >> > >> Yes, or IOMMU backed mdevs. If vfio_dmas in the container are > >> fully > >> pinned and mapped, then the correct dirty page set is all mapped > >> pages. > >> We discussed using the vpfn list as a mechanism for vendor drivers > >> to > >> reduce their migration footprint, but we also discussed that we > >> would > >> need a way to determine that all participants in the container have > >> explicitly pinned their working pages or else we must consider the > >> entire potential working set as dirty. > >> > > > > How can vendor driver tell this capability to iommu module? Any > > suggestions? > > I think it does so by pinning pages. Is it acceptable that if the > vendor driver pins any pages, then from that point forward we > consider > the IOMMU group dirty page scope to be limited to pinned pages? > There > >>> we should also be aware of that dirty page scope is pinned pages + > >>> unpinned pages, > >>> which means ever since a page is pinned, it should be regarded as > >>> dirty > >>> no matter whether it's unpinned later. only after log_sync is called > >>> and > >>> dirty info retrieved, its dirty state should be cleared. > >> > >> Yes, good point. We can't just remove a vpfn when a page is unpinned > >> or else we'd lose information that the page potentially had been > >> dirtied while it was pinned. Maybe that vpfn needs to move to a dirty > >> list and both the currently pinned vpfns and the dirty vpfns are walked > >> on a log_sync. The dirty vpfns list would be cleared after a log_sync. > >> The container would need to know that dirty tracking is enabled and > >> only manage the dirty vpfns list when necessary. Thanks, > >> > > > > If page is unpinned, then that page is available in free page pool for > > others to use, then how can we say that unpinned page has valid data? > > > > If suppose, one driver A unpins a page and when driver B of some other > > device gets that page and he pins it, uses it, and then unpins it, then > > how can we say that page has valid data for driver A? > > > > Can you give one example where unpinned page data is considered reliable > > and valid? > > We can only pin pages that the user has already allocated* and mapped > through the vfio DMA API. The pinning of the page simply locks the > page for the vendor driver to access it and unpinning that page only > indicates that access is complete. Pages are not freed when a vendor > driver unpins them, they still exist and at this point we're now > assuming the device dirtied the page while it was pinned. Thanks, > > Alex > > *
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On 12/5/2019 11:26 AM, Alex Williamson wrote: On Thu, 5 Dec 2019 11:12:23 +0530 Kirti Wankhede wrote: On 12/5/2019 6:58 AM, Yan Zhao wrote: On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: On Wed, 4 Dec 2019 23:40:25 +0530 Kirti Wankhede wrote: On 12/3/2019 11:34 PM, Alex Williamson wrote: On Mon, 25 Nov 2019 19:57:39 -0500 Yan Zhao wrote: On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: On Fri, 15 Nov 2019 00:26:07 +0530 Kirti Wankhede wrote: On 11/14/2019 1:37 AM, Alex Williamson wrote: On Thu, 14 Nov 2019 01:07:21 +0530 Kirti Wankhede wrote: On 11/13/2019 4:00 AM, Alex Williamson wrote: On Tue, 12 Nov 2019 22:33:37 +0530 Kirti Wankhede wrote: All pages pinned by vendor driver through vfio_pin_pages API should be considered as dirty during migration. IOMMU container maintains a list of all such pinned pages. Added an ioctl defination to get bitmap of such definition pinned pages for requested IO virtual address range. Additionally, all mapped pages are considered dirty when physically mapped through to an IOMMU, modulo we discussed devices opting in to per page pinning to indicate finer granularity with a TBD mechanism to figure out if any non-opt-in devices remain. You mean, in case of device direct assignment (device pass through)? Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully pinned and mapped, then the correct dirty page set is all mapped pages. We discussed using the vpfn list as a mechanism for vendor drivers to reduce their migration footprint, but we also discussed that we would need a way to determine that all participants in the container have explicitly pinned their working pages or else we must consider the entire potential working set as dirty. How can vendor driver tell this capability to iommu module? Any suggestions? I think it does so by pinning pages. Is it acceptable that if the vendor driver pins any pages, then from that point forward we consider the IOMMU group dirty page scope to be limited to pinned pages? There we should also be aware of that dirty page scope is pinned pages + unpinned pages, which means ever since a page is pinned, it should be regarded as dirty no matter whether it's unpinned later. only after log_sync is called and dirty info retrieved, its dirty state should be cleared. Yes, good point. We can't just remove a vpfn when a page is unpinned or else we'd lose information that the page potentially had been dirtied while it was pinned. Maybe that vpfn needs to move to a dirty list and both the currently pinned vpfns and the dirty vpfns are walked on a log_sync. The dirty vpfns list would be cleared after a log_sync. The container would need to know that dirty tracking is enabled and only manage the dirty vpfns list when necessary. Thanks, If page is unpinned, then that page is available in free page pool for others to use, then how can we say that unpinned page has valid data? If suppose, one driver A unpins a page and when driver B of some other device gets that page and he pins it, uses it, and then unpins it, then how can we say that page has valid data for driver A? Can you give one example where unpinned page data is considered reliable and valid? We can only pin pages that the user has already allocated* and mapped through the vfio DMA API. The pinning of the page simply locks the page for the vendor driver to access it and unpinning that page only indicates that access is complete. Pages are not freed when a vendor driver unpins them, they still exist and at this point we're now assuming the device dirtied the page while it was pinned. Thanks, Alex * An exception here is that the page might be demand allocated and the act of pinning the page could actually allocate the backing page for the user if they have not faulted the page to trigger that allocation previously. That page remains mapped for the user's virtual address space even after the unpinning though. Yes, I can give an example in GVT. when a gem_object is allocated in guest, before submitting it to guest vGPU, gfx cmds in its ring buffer need to be pinned into GGTT to get a global graphics address for hardware access. At that time, we shadow those cmds and pin pages through vfio pin_pages(), and submit the shadow gem_object to physial hardware. After guest driver thinks the submitted gem_object has completed hardware DMA, it unnpinnd those pinned GGTT graphics memory addresses. Then in host, we unpin the shadow pages through vfio unpin_pages. But, at this point, guest driver is still free to access the gem_object through vCPUs, and guest user space is probably still mapping an object into the gem_object in guest driver. So, missing the dirty page tracking for unpinned pages would cause data inconsitency. If pages are accessed by guest through vCPUs, then RAM module
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, 5 Dec 2019 11:12:23 +0530 Kirti Wankhede wrote: > On 12/5/2019 6:58 AM, Yan Zhao wrote: > > On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: > >> On Wed, 4 Dec 2019 23:40:25 +0530 > >> Kirti Wankhede wrote: > >> > >>> On 12/3/2019 11:34 PM, Alex Williamson wrote: > On Mon, 25 Nov 2019 19:57:39 -0500 > Yan Zhao wrote: > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > >> On Fri, 15 Nov 2019 00:26:07 +0530 > >> Kirti Wankhede wrote: > >> > >>> On 11/14/2019 1:37 AM, Alex Williamson wrote: > On Thu, 14 Nov 2019 01:07:21 +0530 > Kirti Wankhede wrote: > > > On 11/13/2019 4:00 AM, Alex Williamson wrote: > >> On Tue, 12 Nov 2019 22:33:37 +0530 > >> Kirti Wankhede wrote: > >> > >>> All pages pinned by vendor driver through vfio_pin_pages API > >>> should be > >>> considered as dirty during migration. IOMMU container maintains a > >>> list of > >>> all such pinned pages. Added an ioctl defination to get bitmap of > >>> such > >> > >> definition > >> > >>> pinned pages for requested IO virtual address range. > >> > >> Additionally, all mapped pages are considered dirty when physically > >> mapped through to an IOMMU, modulo we discussed devices opting in > >> to > >> per page pinning to indicate finer granularity with a TBD > >> mechanism to > >> figure out if any non-opt-in devices remain. > >> > > > > You mean, in case of device direct assignment (device pass > > through)? > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > pinned and mapped, then the correct dirty page set is all mapped > pages. > We discussed using the vpfn list as a mechanism for vendor drivers to > reduce their migration footprint, but we also discussed that we would > need a way to determine that all participants in the container have > explicitly pinned their working pages or else we must consider the > entire potential working set as dirty. > > >>> > >>> How can vendor driver tell this capability to iommu module? Any > >>> suggestions? > >> > >> I think it does so by pinning pages. Is it acceptable that if the > >> vendor driver pins any pages, then from that point forward we consider > >> the IOMMU group dirty page scope to be limited to pinned pages? There > >> > > we should also be aware of that dirty page scope is pinned pages + > > unpinned pages, > > which means ever since a page is pinned, it should be regarded as dirty > > no matter whether it's unpinned later. only after log_sync is called and > > dirty info retrieved, its dirty state should be cleared. > > Yes, good point. We can't just remove a vpfn when a page is unpinned > or else we'd lose information that the page potentially had been > dirtied while it was pinned. Maybe that vpfn needs to move to a dirty > list and both the currently pinned vpfns and the dirty vpfns are walked > on a log_sync. The dirty vpfns list would be cleared after a log_sync. > The container would need to know that dirty tracking is enabled and > only manage the dirty vpfns list when necessary. Thanks, > > >>> > >>> If page is unpinned, then that page is available in free page pool for > >>> others to use, then how can we say that unpinned page has valid data? > >>> > >>> If suppose, one driver A unpins a page and when driver B of some other > >>> device gets that page and he pins it, uses it, and then unpins it, then > >>> how can we say that page has valid data for driver A? > >>> > >>> Can you give one example where unpinned page data is considered reliable > >>> and valid? > >> > >> We can only pin pages that the user has already allocated* and mapped > >> through the vfio DMA API. The pinning of the page simply locks the > >> page for the vendor driver to access it and unpinning that page only > >> indicates that access is complete. Pages are not freed when a vendor > >> driver unpins them, they still exist and at this point we're now > >> assuming the device dirtied the page while it was pinned. Thanks, > >> > >> Alex > >> > >> * An exception here is that the page might be demand allocated and the > >>act of pinning the page could actually allocate the backing page for > >>the user if they have not faulted the page to trigger that allocation > >>previously. That page remains mapped for the user's virtual address > >>space even after the unpinning though. > >> > > > > Yes, I can give an example in GVT. > > when a gem_object is
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, Dec 05, 2019 at 01:42:23PM +0800, Kirti Wankhede wrote: > > > On 12/5/2019 6:58 AM, Yan Zhao wrote: > > On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: > >> On Wed, 4 Dec 2019 23:40:25 +0530 > >> Kirti Wankhede wrote: > >> > >>> On 12/3/2019 11:34 PM, Alex Williamson wrote: > On Mon, 25 Nov 2019 19:57:39 -0500 > Yan Zhao wrote: > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > >> On Fri, 15 Nov 2019 00:26:07 +0530 > >> Kirti Wankhede wrote: > >> > >>> On 11/14/2019 1:37 AM, Alex Williamson wrote: > On Thu, 14 Nov 2019 01:07:21 +0530 > Kirti Wankhede wrote: > > > On 11/13/2019 4:00 AM, Alex Williamson wrote: > >> On Tue, 12 Nov 2019 22:33:37 +0530 > >> Kirti Wankhede wrote: > >> > >>> All pages pinned by vendor driver through vfio_pin_pages API > >>> should be > >>> considered as dirty during migration. IOMMU container maintains a > >>> list of > >>> all such pinned pages. Added an ioctl defination to get bitmap of > >>> such > >> > >> definition > >> > >>> pinned pages for requested IO virtual address range. > >> > >> Additionally, all mapped pages are considered dirty when physically > >> mapped through to an IOMMU, modulo we discussed devices opting in > >> to > >> per page pinning to indicate finer granularity with a TBD > >> mechanism to > >> figure out if any non-opt-in devices remain. > >> > > > > You mean, in case of device direct assignment (device pass through)? > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > pinned and mapped, then the correct dirty page set is all mapped > pages. > We discussed using the vpfn list as a mechanism for vendor drivers to > reduce their migration footprint, but we also discussed that we would > need a way to determine that all participants in the container have > explicitly pinned their working pages or else we must consider the > entire potential working set as dirty. > > >>> > >>> How can vendor driver tell this capability to iommu module? Any > >>> suggestions? > >> > >> I think it does so by pinning pages. Is it acceptable that if the > >> vendor driver pins any pages, then from that point forward we consider > >> the IOMMU group dirty page scope to be limited to pinned pages? There > > we should also be aware of that dirty page scope is pinned pages + > > unpinned pages, > > which means ever since a page is pinned, it should be regarded as dirty > > no matter whether it's unpinned later. only after log_sync is called and > > dirty info retrieved, its dirty state should be cleared. > > Yes, good point. We can't just remove a vpfn when a page is unpinned > or else we'd lose information that the page potentially had been > dirtied while it was pinned. Maybe that vpfn needs to move to a dirty > list and both the currently pinned vpfns and the dirty vpfns are walked > on a log_sync. The dirty vpfns list would be cleared after a log_sync. > The container would need to know that dirty tracking is enabled and > only manage the dirty vpfns list when necessary. Thanks, > > >>> > >>> If page is unpinned, then that page is available in free page pool for > >>> others to use, then how can we say that unpinned page has valid data? > >>> > >>> If suppose, one driver A unpins a page and when driver B of some other > >>> device gets that page and he pins it, uses it, and then unpins it, then > >>> how can we say that page has valid data for driver A? > >>> > >>> Can you give one example where unpinned page data is considered reliable > >>> and valid? > >> > >> We can only pin pages that the user has already allocated* and mapped > >> through the vfio DMA API. The pinning of the page simply locks the > >> page for the vendor driver to access it and unpinning that page only > >> indicates that access is complete. Pages are not freed when a vendor > >> driver unpins them, they still exist and at this point we're now > >> assuming the device dirtied the page while it was pinned. Thanks, > >> > >> Alex > >> > >> * An exception here is that the page might be demand allocated and the > >>act of pinning the page could actually allocate the backing page for > >>the user if they have not faulted the page to trigger that allocation > >>previously. That page remains mapped for the user's virtual address > >>space even after the unpinning though. > >> > > > > Yes, I can give an example in GVT. > > when a gem_object is allocated in guest, before submitting it to guest > > vGPU,
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On 12/5/2019 6:58 AM, Yan Zhao wrote: On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: On Wed, 4 Dec 2019 23:40:25 +0530 Kirti Wankhede wrote: On 12/3/2019 11:34 PM, Alex Williamson wrote: On Mon, 25 Nov 2019 19:57:39 -0500 Yan Zhao wrote: On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: On Fri, 15 Nov 2019 00:26:07 +0530 Kirti Wankhede wrote: On 11/14/2019 1:37 AM, Alex Williamson wrote: On Thu, 14 Nov 2019 01:07:21 +0530 Kirti Wankhede wrote: On 11/13/2019 4:00 AM, Alex Williamson wrote: On Tue, 12 Nov 2019 22:33:37 +0530 Kirti Wankhede wrote: All pages pinned by vendor driver through vfio_pin_pages API should be considered as dirty during migration. IOMMU container maintains a list of all such pinned pages. Added an ioctl defination to get bitmap of such definition pinned pages for requested IO virtual address range. Additionally, all mapped pages are considered dirty when physically mapped through to an IOMMU, modulo we discussed devices opting in to per page pinning to indicate finer granularity with a TBD mechanism to figure out if any non-opt-in devices remain. You mean, in case of device direct assignment (device pass through)? Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully pinned and mapped, then the correct dirty page set is all mapped pages. We discussed using the vpfn list as a mechanism for vendor drivers to reduce their migration footprint, but we also discussed that we would need a way to determine that all participants in the container have explicitly pinned their working pages or else we must consider the entire potential working set as dirty. How can vendor driver tell this capability to iommu module? Any suggestions? I think it does so by pinning pages. Is it acceptable that if the vendor driver pins any pages, then from that point forward we consider the IOMMU group dirty page scope to be limited to pinned pages? There we should also be aware of that dirty page scope is pinned pages + unpinned pages, which means ever since a page is pinned, it should be regarded as dirty no matter whether it's unpinned later. only after log_sync is called and dirty info retrieved, its dirty state should be cleared. Yes, good point. We can't just remove a vpfn when a page is unpinned or else we'd lose information that the page potentially had been dirtied while it was pinned. Maybe that vpfn needs to move to a dirty list and both the currently pinned vpfns and the dirty vpfns are walked on a log_sync. The dirty vpfns list would be cleared after a log_sync. The container would need to know that dirty tracking is enabled and only manage the dirty vpfns list when necessary. Thanks, If page is unpinned, then that page is available in free page pool for others to use, then how can we say that unpinned page has valid data? If suppose, one driver A unpins a page and when driver B of some other device gets that page and he pins it, uses it, and then unpins it, then how can we say that page has valid data for driver A? Can you give one example where unpinned page data is considered reliable and valid? We can only pin pages that the user has already allocated* and mapped through the vfio DMA API. The pinning of the page simply locks the page for the vendor driver to access it and unpinning that page only indicates that access is complete. Pages are not freed when a vendor driver unpins them, they still exist and at this point we're now assuming the device dirtied the page while it was pinned. Thanks, Alex * An exception here is that the page might be demand allocated and the act of pinning the page could actually allocate the backing page for the user if they have not faulted the page to trigger that allocation previously. That page remains mapped for the user's virtual address space even after the unpinning though. Yes, I can give an example in GVT. when a gem_object is allocated in guest, before submitting it to guest vGPU, gfx cmds in its ring buffer need to be pinned into GGTT to get a global graphics address for hardware access. At that time, we shadow those cmds and pin pages through vfio pin_pages(), and submit the shadow gem_object to physial hardware. After guest driver thinks the submitted gem_object has completed hardware DMA, it unnpinnd those pinned GGTT graphics memory addresses. Then in host, we unpin the shadow pages through vfio unpin_pages. But, at this point, guest driver is still free to access the gem_object through vCPUs, and guest user space is probably still mapping an object into the gem_object in guest driver. So, missing the dirty page tracking for unpinned pages would cause data inconsitency. If pages are accessed by guest through vCPUs, then RAM module in QEMU will take care of tracking those pages as dirty. All unpinned pages might not be used, so tracking all unpinned pages during VM
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, Dec 05, 2019 at 02:34:57AM +0800, Alex Williamson wrote: > On Wed, 4 Dec 2019 23:40:25 +0530 > Kirti Wankhede wrote: > > > On 12/3/2019 11:34 PM, Alex Williamson wrote: > > > On Mon, 25 Nov 2019 19:57:39 -0500 > > > Yan Zhao wrote: > > > > > >> On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > >>> On Fri, 15 Nov 2019 00:26:07 +0530 > > >>> Kirti Wankhede wrote: > > >>> > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > Kirti Wankhede wrote: > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > >>> Kirti Wankhede wrote: > > >>> > > All pages pinned by vendor driver through vfio_pin_pages API > > should be > > considered as dirty during migration. IOMMU container maintains a > > list of > > all such pinned pages. Added an ioctl defination to get bitmap of > > such > > >>> > > >>> definition > > >>> > > pinned pages for requested IO virtual address range. > > >>> > > >>> Additionally, all mapped pages are considered dirty when physically > > >>> mapped through to an IOMMU, modulo we discussed devices opting in to > > >>> per page pinning to indicate finer granularity with a TBD mechanism > > >>> to > > >>> figure out if any non-opt-in devices remain. > > >>> > > >> > > >> You mean, in case of device direct assignment (device pass through)? > > >> > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > > > pinned and mapped, then the correct dirty page set is all mapped > > > pages. > > > We discussed using the vpfn list as a mechanism for vendor drivers to > > > reduce their migration footprint, but we also discussed that we would > > > need a way to determine that all participants in the container have > > > explicitly pinned their working pages or else we must consider the > > > entire potential working set as dirty. > > > > > > > How can vendor driver tell this capability to iommu module? Any > > suggestions? > > >>> > > >>> I think it does so by pinning pages. Is it acceptable that if the > > >>> vendor driver pins any pages, then from that point forward we consider > > >>> the IOMMU group dirty page scope to be limited to pinned pages? There > > >> we should also be aware of that dirty page scope is pinned pages + > > >> unpinned pages, > > >> which means ever since a page is pinned, it should be regarded as dirty > > >> no matter whether it's unpinned later. only after log_sync is called and > > >> dirty info retrieved, its dirty state should be cleared. > > > > > > Yes, good point. We can't just remove a vpfn when a page is unpinned > > > or else we'd lose information that the page potentially had been > > > dirtied while it was pinned. Maybe that vpfn needs to move to a dirty > > > list and both the currently pinned vpfns and the dirty vpfns are walked > > > on a log_sync. The dirty vpfns list would be cleared after a log_sync. > > > The container would need to know that dirty tracking is enabled and > > > only manage the dirty vpfns list when necessary. Thanks, > > > > > > > If page is unpinned, then that page is available in free page pool for > > others to use, then how can we say that unpinned page has valid data? > > > > If suppose, one driver A unpins a page and when driver B of some other > > device gets that page and he pins it, uses it, and then unpins it, then > > how can we say that page has valid data for driver A? > > > > Can you give one example where unpinned page data is considered reliable > > and valid? > > We can only pin pages that the user has already allocated* and mapped > through the vfio DMA API. The pinning of the page simply locks the > page for the vendor driver to access it and unpinning that page only > indicates that access is complete. Pages are not freed when a vendor > driver unpins them, they still exist and at this point we're now > assuming the device dirtied the page while it was pinned. Thanks, > > Alex > > * An exception here is that the page might be demand allocated and the > act of pinning the page could actually allocate the backing page for > the user if they have not faulted the page to trigger that allocation > previously. That page remains mapped for the user's virtual address > space even after the unpinning though. > Yes, I can give an example in GVT. when a gem_object is allocated in guest, before submitting it to guest vGPU, gfx cmds in its ring buffer need to be pinned into GGTT to get a global graphics address for hardware access. At that time, we shadow those cmds and pin pages through vfio pin_pages(), and submit the shadow gem_object to physial hardware. After guest driver
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Wed, 4 Dec 2019 23:40:25 +0530 Kirti Wankhede wrote: > On 12/3/2019 11:34 PM, Alex Williamson wrote: > > On Mon, 25 Nov 2019 19:57:39 -0500 > > Yan Zhao wrote: > > > >> On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > >>> On Fri, 15 Nov 2019 00:26:07 +0530 > >>> Kirti Wankhede wrote: > >>> > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > On Thu, 14 Nov 2019 01:07:21 +0530 > > Kirti Wankhede wrote: > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > >>> Kirti Wankhede wrote: > >>> > All pages pinned by vendor driver through vfio_pin_pages API should > be > considered as dirty during migration. IOMMU container maintains a > list of > all such pinned pages. Added an ioctl defination to get bitmap of > such > >>> > >>> definition > >>> > pinned pages for requested IO virtual address range. > >>> > >>> Additionally, all mapped pages are considered dirty when physically > >>> mapped through to an IOMMU, modulo we discussed devices opting in to > >>> per page pinning to indicate finer granularity with a TBD mechanism to > >>> figure out if any non-opt-in devices remain. > >>> > >> > >> You mean, in case of device direct assignment (device pass through)? > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > > pinned and mapped, then the correct dirty page set is all mapped pages. > > We discussed using the vpfn list as a mechanism for vendor drivers to > > reduce their migration footprint, but we also discussed that we would > > need a way to determine that all participants in the container have > > explicitly pinned their working pages or else we must consider the > > entire potential working set as dirty. > > > > How can vendor driver tell this capability to iommu module? Any > suggestions? > >>> > >>> I think it does so by pinning pages. Is it acceptable that if the > >>> vendor driver pins any pages, then from that point forward we consider > >>> the IOMMU group dirty page scope to be limited to pinned pages? There > >> we should also be aware of that dirty page scope is pinned pages + > >> unpinned pages, > >> which means ever since a page is pinned, it should be regarded as dirty > >> no matter whether it's unpinned later. only after log_sync is called and > >> dirty info retrieved, its dirty state should be cleared. > > > > Yes, good point. We can't just remove a vpfn when a page is unpinned > > or else we'd lose information that the page potentially had been > > dirtied while it was pinned. Maybe that vpfn needs to move to a dirty > > list and both the currently pinned vpfns and the dirty vpfns are walked > > on a log_sync. The dirty vpfns list would be cleared after a log_sync. > > The container would need to know that dirty tracking is enabled and > > only manage the dirty vpfns list when necessary. Thanks, > > > > If page is unpinned, then that page is available in free page pool for > others to use, then how can we say that unpinned page has valid data? > > If suppose, one driver A unpins a page and when driver B of some other > device gets that page and he pins it, uses it, and then unpins it, then > how can we say that page has valid data for driver A? > > Can you give one example where unpinned page data is considered reliable > and valid? We can only pin pages that the user has already allocated* and mapped through the vfio DMA API. The pinning of the page simply locks the page for the vendor driver to access it and unpinning that page only indicates that access is complete. Pages are not freed when a vendor driver unpins them, they still exist and at this point we're now assuming the device dirtied the page while it was pinned. Thanks, Alex * An exception here is that the page might be demand allocated and the act of pinning the page could actually allocate the backing page for the user if they have not faulted the page to trigger that allocation previously. That page remains mapped for the user's virtual address space even after the unpinning though.
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On 12/3/2019 11:34 PM, Alex Williamson wrote:
On Mon, 25 Nov 2019 19:57:39 -0500
Yan Zhao wrote:
On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote:
On Fri, 15 Nov 2019 00:26:07 +0530
Kirti Wankhede wrote:
On 11/14/2019 1:37 AM, Alex Williamson wrote:
On Thu, 14 Nov 2019 01:07:21 +0530
Kirti Wankhede wrote:
On 11/13/2019 4:00 AM, Alex Williamson wrote:
On Tue, 12 Nov 2019 22:33:37 +0530
Kirti Wankhede wrote:
All pages pinned by vendor driver through vfio_pin_pages API should be
considered as dirty during migration. IOMMU container maintains a list of
all such pinned pages. Added an ioctl defination to get bitmap of such
definition
pinned pages for requested IO virtual address range.
Additionally, all mapped pages are considered dirty when physically
mapped through to an IOMMU, modulo we discussed devices opting in to
per page pinning to indicate finer granularity with a TBD mechanism to
figure out if any non-opt-in devices remain.
You mean, in case of device direct assignment (device pass through)?
Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
pinned and mapped, then the correct dirty page set is all mapped pages.
We discussed using the vpfn list as a mechanism for vendor drivers to
reduce their migration footprint, but we also discussed that we would
need a way to determine that all participants in the container have
explicitly pinned their working pages or else we must consider the
entire potential working set as dirty.
How can vendor driver tell this capability to iommu module? Any suggestions?
I think it does so by pinning pages. Is it acceptable that if the
vendor driver pins any pages, then from that point forward we consider
the IOMMU group dirty page scope to be limited to pinned pages? There
we should also be aware of that dirty page scope is pinned pages + unpinned
pages,
which means ever since a page is pinned, it should be regarded as dirty
no matter whether it's unpinned later. only after log_sync is called and
dirty info retrieved, its dirty state should be cleared.
Yes, good point. We can't just remove a vpfn when a page is unpinned
or else we'd lose information that the page potentially had been
dirtied while it was pinned. Maybe that vpfn needs to move to a dirty
list and both the currently pinned vpfns and the dirty vpfns are walked
on a log_sync. The dirty vpfns list would be cleared after a log_sync.
The container would need to know that dirty tracking is enabled and
only manage the dirty vpfns list when necessary. Thanks,
If page is unpinned, then that page is available in free page pool for
others to use, then how can we say that unpinned page has valid data?
If suppose, one driver A unpins a page and when driver B of some other
device gets that page and he pins it, uses it, and then unpins it, then
how can we say that page has valid data for driver A?
Can you give one example where unpinned page data is considered reliable
and valid?
Thanks,
Kirti
Alex
are complications around non-singleton IOMMU groups, but I think we're
already leaning towards that being a non-worthwhile problem to solve.
So if we require that only singleton IOMMU groups can pin pages and we
pass the IOMMU group as a parameter to
vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a
flag on its local vfio_group struct to indicate dirty page scope is
limited to pinned pages. We might want to keep a flag on the
vfio_iommu struct to indicate if all of the vfio_groups for each
vfio_domain in the vfio_iommu.domain_list dirty page scope limited to
pinned pages as an optimization to avoid walking lists too often. Then
we could test if vfio_iommu.domain_list is not empty and this new flag
does not limit the dirty page scope, then everything within each
vfio_dma is considered dirty.
Signed-off-by: Kirti Wankhede
Reviewed-by: Neo Jia
---
include/uapi/linux/vfio.h | 23 +++
1 file changed, 23 insertions(+)
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 35b09427ad9f..6fd3822aa610 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
#define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
#define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
+/**
+ * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
+ * struct vfio_iommu_type1_dirty_bitmap)
+ *
+ * IOCTL to get dirty pages bitmap for IOMMU container during migration.
+ * Get dirty pages bitmap of given IO virtual addresses range using
+ * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is size of
+ * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to get
+ * bitmap and should set size of allocated memory in bitmap_size field.
+ * One bit is used to represent per page consecutively starting
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Mon, 25 Nov 2019 19:57:39 -0500
Yan Zhao wrote:
> On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote:
> > On Fri, 15 Nov 2019 00:26:07 +0530
> > Kirti Wankhede wrote:
> >
> > > On 11/14/2019 1:37 AM, Alex Williamson wrote:
> > > > On Thu, 14 Nov 2019 01:07:21 +0530
> > > > Kirti Wankhede wrote:
> > > >
> > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote:
> > > >>> On Tue, 12 Nov 2019 22:33:37 +0530
> > > >>> Kirti Wankhede wrote:
> > > >>>
> > > All pages pinned by vendor driver through vfio_pin_pages API should
> > > be
> > > considered as dirty during migration. IOMMU container maintains a
> > > list of
> > > all such pinned pages. Added an ioctl defination to get bitmap of
> > > such
> > > >>>
> > > >>> definition
> > > >>>
> > > pinned pages for requested IO virtual address range.
> > > >>>
> > > >>> Additionally, all mapped pages are considered dirty when physically
> > > >>> mapped through to an IOMMU, modulo we discussed devices opting in to
> > > >>> per page pinning to indicate finer granularity with a TBD mechanism to
> > > >>> figure out if any non-opt-in devices remain.
> > > >>>
> > > >>
> > > >> You mean, in case of device direct assignment (device pass through)?
> > > >>
> > > >
> > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
> > > > pinned and mapped, then the correct dirty page set is all mapped pages.
> > > > We discussed using the vpfn list as a mechanism for vendor drivers to
> > > > reduce their migration footprint, but we also discussed that we would
> > > > need a way to determine that all participants in the container have
> > > > explicitly pinned their working pages or else we must consider the
> > > > entire potential working set as dirty.
> > > >
> > >
> > > How can vendor driver tell this capability to iommu module? Any
> > > suggestions?
> >
> > I think it does so by pinning pages. Is it acceptable that if the
> > vendor driver pins any pages, then from that point forward we consider
> > the IOMMU group dirty page scope to be limited to pinned pages? There
> we should also be aware of that dirty page scope is pinned pages + unpinned
> pages,
> which means ever since a page is pinned, it should be regarded as dirty
> no matter whether it's unpinned later. only after log_sync is called and
> dirty info retrieved, its dirty state should be cleared.
Yes, good point. We can't just remove a vpfn when a page is unpinned
or else we'd lose information that the page potentially had been
dirtied while it was pinned. Maybe that vpfn needs to move to a dirty
list and both the currently pinned vpfns and the dirty vpfns are walked
on a log_sync. The dirty vpfns list would be cleared after a log_sync.
The container would need to know that dirty tracking is enabled and
only manage the dirty vpfns list when necessary. Thanks,
Alex
> > are complications around non-singleton IOMMU groups, but I think we're
> > already leaning towards that being a non-worthwhile problem to solve.
> > So if we require that only singleton IOMMU groups can pin pages and we
> > pass the IOMMU group as a parameter to
> > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a
> > flag on its local vfio_group struct to indicate dirty page scope is
> > limited to pinned pages. We might want to keep a flag on the
> > vfio_iommu struct to indicate if all of the vfio_groups for each
> > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to
> > pinned pages as an optimization to avoid walking lists too often. Then
> > we could test if vfio_iommu.domain_list is not empty and this new flag
> > does not limit the dirty page scope, then everything within each
> > vfio_dma is considered dirty.
> >
> > > Signed-off-by: Kirti Wankhede
> > > Reviewed-by: Neo Jia
> > > ---
> > > include/uapi/linux/vfio.h | 23 +++
> > > 1 file changed, 23 insertions(+)
> > >
> > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > > index 35b09427ad9f..6fd3822aa610 100644
> > > --- a/include/uapi/linux/vfio.h
> > > +++ b/include/uapi/linux/vfio.h
> > > @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> > > #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> > > #define VFIO_IOMMU_DISABLE_IO(VFIO_TYPE, VFIO_BASE + 16)
> > >
> > > +/**
> > > + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> > > + * struct
> > > vfio_iommu_type1_dirty_bitmap)
> > > + *
> > > + * IOCTL to get dirty pages bitmap for IOMMU container during
> > > migration.
> > > + * Get dirty pages bitmap of given IO virtual addresses range using
> > > + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which
> > > is size of
> > >
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote:
> On Fri, 15 Nov 2019 00:26:07 +0530
> Kirti Wankhede wrote:
>
> > On 11/14/2019 1:37 AM, Alex Williamson wrote:
> > > On Thu, 14 Nov 2019 01:07:21 +0530
> > > Kirti Wankhede wrote:
> > >
> > >> On 11/13/2019 4:00 AM, Alex Williamson wrote:
> > >>> On Tue, 12 Nov 2019 22:33:37 +0530
> > >>> Kirti Wankhede wrote:
> > >>>
> > All pages pinned by vendor driver through vfio_pin_pages API should be
> > considered as dirty during migration. IOMMU container maintains a list
> > of
> > all such pinned pages. Added an ioctl defination to get bitmap of such
> >
> > >>>
> > >>> definition
> > >>>
> > pinned pages for requested IO virtual address range.
> > >>>
> > >>> Additionally, all mapped pages are considered dirty when physically
> > >>> mapped through to an IOMMU, modulo we discussed devices opting in to
> > >>> per page pinning to indicate finer granularity with a TBD mechanism to
> > >>> figure out if any non-opt-in devices remain.
> > >>>
> > >>
> > >> You mean, in case of device direct assignment (device pass through)?
> > >
> > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
> > > pinned and mapped, then the correct dirty page set is all mapped pages.
> > > We discussed using the vpfn list as a mechanism for vendor drivers to
> > > reduce their migration footprint, but we also discussed that we would
> > > need a way to determine that all participants in the container have
> > > explicitly pinned their working pages or else we must consider the
> > > entire potential working set as dirty.
> > >
> >
> > How can vendor driver tell this capability to iommu module? Any suggestions?
>
> I think it does so by pinning pages. Is it acceptable that if the
> vendor driver pins any pages, then from that point forward we consider
> the IOMMU group dirty page scope to be limited to pinned pages? There
we should also be aware of that dirty page scope is pinned pages + unpinned
pages,
which means ever since a page is pinned, it should be regarded as dirty
no matter whether it's unpinned later. only after log_sync is called and
dirty info retrieved, its dirty state should be cleared.
> are complications around non-singleton IOMMU groups, but I think we're
> already leaning towards that being a non-worthwhile problem to solve.
> So if we require that only singleton IOMMU groups can pin pages and we
> pass the IOMMU group as a parameter to
> vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a
> flag on its local vfio_group struct to indicate dirty page scope is
> limited to pinned pages. We might want to keep a flag on the
> vfio_iommu struct to indicate if all of the vfio_groups for each
> vfio_domain in the vfio_iommu.domain_list dirty page scope limited to
> pinned pages as an optimization to avoid walking lists too often. Then
> we could test if vfio_iommu.domain_list is not empty and this new flag
> does not limit the dirty page scope, then everything within each
> vfio_dma is considered dirty.
>
> > Signed-off-by: Kirti Wankhede
> > Reviewed-by: Neo Jia
> > ---
> > include/uapi/linux/vfio.h | 23 +++
> > 1 file changed, 23 insertions(+)
> >
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 35b09427ad9f..6fd3822aa610 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> > #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> > #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
> >
> > +/**
> > + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> > + * struct
> > vfio_iommu_type1_dirty_bitmap)
> > + *
> > + * IOCTL to get dirty pages bitmap for IOMMU container during
> > migration.
> > + * Get dirty pages bitmap of given IO virtual addresses range using
> > + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is
> > size of
> > + * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory
> > to get
> > + * bitmap and should set size of allocated memory in bitmap_size
> > field.
> > + * One bit is used to represent per page consecutively starting from
> > iova
> > + * offset. Bit set indicates page at that offset from iova is dirty.
> > + */
> > +struct vfio_iommu_type1_dirty_bitmap {
> > + __u32argsz;
> > + __u32flags;
> > + __u64iova; /* IO virtual address */
> > + __u64size; /* Size of iova range */
> > + __u64bitmap_size; /* in bytes */
> > >>>
> > >>> This seems redundant. We can
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Fri, Nov 15, 2019 at 11:21:33AM +0800, Alex Williamson wrote: > On Thu, 14 Nov 2019 21:40:35 -0500 > Yan Zhao wrote: > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > > On Fri, 15 Nov 2019 00:26:07 +0530 > > > Kirti Wankhede wrote: > > > > > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > > > Kirti Wankhede wrote: > > > > > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > > > >>> Kirti Wankhede wrote: > > > > >>> > > > > All pages pinned by vendor driver through vfio_pin_pages API > > > > should be > > > > considered as dirty during migration. IOMMU container maintains a > > > > list of > > > > all such pinned pages. Added an ioctl defination to get bitmap of > > > > such > > > > >>> > > > > >>> definition > > > > >>> > > > > pinned pages for requested IO virtual address range. > > > > >>> > > > > >>> Additionally, all mapped pages are considered dirty when physically > > > > >>> mapped through to an IOMMU, modulo we discussed devices opting in to > > > > >>> per page pinning to indicate finer granularity with a TBD mechanism > > > > >>> to > > > > >>> figure out if any non-opt-in devices remain. > > > > >>> > > > > >> > > > > >> You mean, in case of device direct assignment (device pass through)? > > > > >> > > > > > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > > > > > pinned and mapped, then the correct dirty page set is all mapped > > > > > pages. > > > > > We discussed using the vpfn list as a mechanism for vendor drivers to > > > > > reduce their migration footprint, but we also discussed that we would > > > > > need a way to determine that all participants in the container have > > > > > explicitly pinned their working pages or else we must consider the > > > > > entire potential working set as dirty. > > > > > > > > > > > > > How can vendor driver tell this capability to iommu module? Any > > > > suggestions? > > > > > > I think it does so by pinning pages. Is it acceptable that if the > > > vendor driver pins any pages, then from that point forward we consider > > > the IOMMU group dirty page scope to be limited to pinned pages? There > > > are complications around non-singleton IOMMU groups, but I think we're > > > already leaning towards that being a non-worthwhile problem to solve. > > > So if we require that only singleton IOMMU groups can pin pages and we > > > pass the IOMMU group as a parameter to > > > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a > > > flag on its local vfio_group struct to indicate dirty page scope is > > > limited to pinned pages. We might want to keep a flag on the > > > vfio_iommu struct to indicate if all of the vfio_groups for each > > > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to > > > pinned pages as an optimization to avoid walking lists too often. Then > > > we could test if vfio_iommu.domain_list is not empty and this new flag > > > does not limit the dirty page scope, then everything within each > > > vfio_dma is considered dirty. > > > > > > > hi Alex > > could you help clarify whether my understandings below are right? > > In future, > > 1. for mdev and for passthrough device withoug hardware ability to track > > dirty pages, the vendor driver has to explicitly call > > vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page > > set. > > For non-IOMMU backed mdevs without hardware dirty page tracking, > there's no change to the vendor driver currently. Pages pinned by the > vendor driver are marked as dirty. > > For any IOMMU backed device, mdev or direct assignment, all mapped > memory would be considered dirty unless there are explicit calls to pin > pages on top of the IOMMU page pinning and mapping. These would likely > be enabled only when the device is in the _SAVING device_state. > > > 2. for those devices with hardware ability to track dirty pages, will still > > provide a callback to vendor driver to get dirty pages. (as for those > > devices, > > it is hard to explicitly call vfio_pin_pages()/vfio_unpin_pages()) > > > > 3. for devices relying on dirty bit info in physical IOMMU, there > > will be a callback to physical IOMMU driver to get dirty page set from > > vfio. > > The proposal here does not cover exactly how these would be > implemented, it only establishes the container as the point of user > interaction with the dirty bitmap and hopefully allows us to maintain > that interface regardless of whether we have dirty tracking at the > device or the system IOMMU. Ideally devices with dirty tracking would > make use of page pinning and we'd extend the interface to allow vendor > drivers the ability to indicate the clean/dirty state of those pinned > pages. For system IOMMU dirty page
RE: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
> From: Alex Williamson [mailto:alex.william...@redhat.com] > Sent: Wednesday, November 20, 2019 7:17 AM > > On Fri, 15 Nov 2019 05:10:53 + > "Tian, Kevin" wrote: > > > > From: Alex Williamson > > > Sent: Friday, November 15, 2019 11:22 AM > > > > > > On Thu, 14 Nov 2019 21:40:35 -0500 > > > Yan Zhao wrote: > > > > > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > > > > On Fri, 15 Nov 2019 00:26:07 +0530 > > > > > Kirti Wankhede wrote: > > > > > > > > > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > > > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > > > > > Kirti Wankhede wrote: > > > > > > > > > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > > > > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > > > > > >>> Kirti Wankhede wrote: > > > > > > >>> > > > > > > All pages pinned by vendor driver through vfio_pin_pages > API > > > should be > > > > > > considered as dirty during migration. IOMMU container > > > maintains a list of > > > > > > all such pinned pages. Added an ioctl defination to get > bitmap of > > > such > > > > > > >>> > > > > > > >>> definition > > > > > > >>> > > > > > > pinned pages for requested IO virtual address range. > > > > > > >>> > > > > > > >>> Additionally, all mapped pages are considered dirty when > > > physically > > > > > > >>> mapped through to an IOMMU, modulo we discussed devices > > > opting in to > > > > > > >>> per page pinning to indicate finer granularity with a TBD > > > mechanism to > > > > > > >>> figure out if any non-opt-in devices remain. > > > > > > >>> > > > > > > >> > > > > > > >> You mean, in case of device direct assignment (device pass > > > through)? > > > > > > > > > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are > > > fully > > > > > > > pinned and mapped, then the correct dirty page set is all > mapped > > > pages. > > > > > > > We discussed using the vpfn list as a mechanism for vendor > drivers > > > to > > > > > > > reduce their migration footprint, but we also discussed that we > > > would > > > > > > > need a way to determine that all participants in the container > have > > > > > > > explicitly pinned their working pages or else we must consider > the > > > > > > > entire potential working set as dirty. > > > > > > > > > > > > > > > > > > > How can vendor driver tell this capability to iommu module? Any > > > suggestions? > > > > > > > > > > I think it does so by pinning pages. Is it acceptable that if the > > > > > vendor driver pins any pages, then from that point forward we > consider > > > > > the IOMMU group dirty page scope to be limited to pinned pages? > > > There > > > > > are complications around non-singleton IOMMU groups, but I think > > > we're > > > > > already leaning towards that being a non-worthwhile problem to > solve. > > > > > So if we require that only singleton IOMMU groups can pin pages > and > > > we > > > > > pass the IOMMU group as a parameter to > > > > > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can > set a > > > > > flag on its local vfio_group struct to indicate dirty page scope is > > > > > limited to pinned pages. We might want to keep a flag on the > > > > > vfio_iommu struct to indicate if all of the vfio_groups for each > > > > > vfio_domain in the vfio_iommu.domain_list dirty page scope limited > to > > > > > pinned pages as an optimization to avoid walking lists too often. > Then > > > > > we could test if vfio_iommu.domain_list is not empty and this new > flag > > > > > does not limit the dirty page scope, then everything within each > > > > > vfio_dma is considered dirty. > > > > > > > > > > > > > hi Alex > > > > could you help clarify whether my understandings below are right? > > > > In future, > > > > 1. for mdev and for passthrough device withoug hardware ability to > track > > > > dirty pages, the vendor driver has to explicitly call > > > > vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page > set. > > > > > > For non-IOMMU backed mdevs without hardware dirty page tracking, > > > there's no change to the vendor driver currently. Pages pinned by the > > > vendor driver are marked as dirty. > > > > What about the vendor driver can figure out, in software means, which > > pinned pages are actually dirty? In that case, would a separate mark_dirty > > interface make more sense? Or introduce read/write flag to the > pin_pages > > interface similar to DMA API? Existing drivers always set both r/w flags > but > > just in case then a specific driver may set read-only or write-only... > > You're jumping ahead to 2. below, where my reply is that we need to They are different. 2) is about hardware support which may collect dirty page info in a log buffer and then report to driver when the latter requests. Here I'm talking about software approach, i.e. when the vendor driver intercepts certain guest operations, it may figure out whether the captured DMA pages are used for write
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Fri, 15 Nov 2019 05:10:53 + "Tian, Kevin" wrote: > > From: Alex Williamson > > Sent: Friday, November 15, 2019 11:22 AM > > > > On Thu, 14 Nov 2019 21:40:35 -0500 > > Yan Zhao wrote: > > > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > > > On Fri, 15 Nov 2019 00:26:07 +0530 > > > > Kirti Wankhede wrote: > > > > > > > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > > > > Kirti Wankhede wrote: > > > > > > > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > > > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > > > > >>> Kirti Wankhede wrote: > > > > > >>> > > > > > All pages pinned by vendor driver through vfio_pin_pages API > > should be > > > > > considered as dirty during migration. IOMMU container > > maintains a list of > > > > > all such pinned pages. Added an ioctl defination to get bitmap > > > > > of > > such > > > > > >>> > > > > > >>> definition > > > > > >>> > > > > > pinned pages for requested IO virtual address range. > > > > > >>> > > > > > >>> Additionally, all mapped pages are considered dirty when > > physically > > > > > >>> mapped through to an IOMMU, modulo we discussed devices > > opting in to > > > > > >>> per page pinning to indicate finer granularity with a TBD > > mechanism to > > > > > >>> figure out if any non-opt-in devices remain. > > > > > >>> > > > > > >> > > > > > >> You mean, in case of device direct assignment (device pass > > through)? > > > > > > > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are > > fully > > > > > > pinned and mapped, then the correct dirty page set is all mapped > > pages. > > > > > > We discussed using the vpfn list as a mechanism for vendor drivers > > to > > > > > > reduce their migration footprint, but we also discussed that we > > would > > > > > > need a way to determine that all participants in the container have > > > > > > explicitly pinned their working pages or else we must consider the > > > > > > entire potential working set as dirty. > > > > > > > > > > > > > > > > How can vendor driver tell this capability to iommu module? Any > > suggestions? > > > > > > > > I think it does so by pinning pages. Is it acceptable that if the > > > > vendor driver pins any pages, then from that point forward we consider > > > > the IOMMU group dirty page scope to be limited to pinned pages? > > There > > > > are complications around non-singleton IOMMU groups, but I think > > we're > > > > already leaning towards that being a non-worthwhile problem to solve. > > > > So if we require that only singleton IOMMU groups can pin pages and > > we > > > > pass the IOMMU group as a parameter to > > > > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a > > > > flag on its local vfio_group struct to indicate dirty page scope is > > > > limited to pinned pages. We might want to keep a flag on the > > > > vfio_iommu struct to indicate if all of the vfio_groups for each > > > > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to > > > > pinned pages as an optimization to avoid walking lists too often. Then > > > > we could test if vfio_iommu.domain_list is not empty and this new flag > > > > does not limit the dirty page scope, then everything within each > > > > vfio_dma is considered dirty. > > > > > > > > > > hi Alex > > > could you help clarify whether my understandings below are right? > > > In future, > > > 1. for mdev and for passthrough device withoug hardware ability to track > > > dirty pages, the vendor driver has to explicitly call > > > vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page > > > set. > > > > For non-IOMMU backed mdevs without hardware dirty page tracking, > > there's no change to the vendor driver currently. Pages pinned by the > > vendor driver are marked as dirty. > > What about the vendor driver can figure out, in software means, which > pinned pages are actually dirty? In that case, would a separate mark_dirty > interface make more sense? Or introduce read/write flag to the pin_pages > interface similar to DMA API? Existing drivers always set both r/w flags but > just in case then a specific driver may set read-only or write-only... You're jumping ahead to 2. below, where my reply is that we need to extend the interface to allow the vendor driver to manipulate clean/dirty state. I don't know exactly what those interfaces should look like, but yes, something should exist to allow that control. If the default is to mark pinned pages dirty, then we might need a separate pin_pages_clean callback. > > For any IOMMU backed device, mdev or direct assignment, all mapped > > memory would be considered dirty unless there are explicit calls to pin > > pages on top of the IOMMU page pinning and mapping. These would likely > > be enabled only when
RE: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
> From: Alex Williamson > Sent: Friday, November 15, 2019 11:22 AM > > On Thu, 14 Nov 2019 21:40:35 -0500 > Yan Zhao wrote: > > > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > > On Fri, 15 Nov 2019 00:26:07 +0530 > > > Kirti Wankhede wrote: > > > > > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > > > Kirti Wankhede wrote: > > > > > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > > > >>> Kirti Wankhede wrote: > > > > >>> > > > > All pages pinned by vendor driver through vfio_pin_pages API > should be > > > > considered as dirty during migration. IOMMU container > maintains a list of > > > > all such pinned pages. Added an ioctl defination to get bitmap of > such > > > > >>> > > > > >>> definition > > > > >>> > > > > pinned pages for requested IO virtual address range. > > > > >>> > > > > >>> Additionally, all mapped pages are considered dirty when > physically > > > > >>> mapped through to an IOMMU, modulo we discussed devices > opting in to > > > > >>> per page pinning to indicate finer granularity with a TBD > mechanism to > > > > >>> figure out if any non-opt-in devices remain. > > > > >>> > > > > >> > > > > >> You mean, in case of device direct assignment (device pass > through)? > > > > > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are > fully > > > > > pinned and mapped, then the correct dirty page set is all mapped > pages. > > > > > We discussed using the vpfn list as a mechanism for vendor drivers > to > > > > > reduce their migration footprint, but we also discussed that we > would > > > > > need a way to determine that all participants in the container have > > > > > explicitly pinned their working pages or else we must consider the > > > > > entire potential working set as dirty. > > > > > > > > > > > > > How can vendor driver tell this capability to iommu module? Any > suggestions? > > > > > > I think it does so by pinning pages. Is it acceptable that if the > > > vendor driver pins any pages, then from that point forward we consider > > > the IOMMU group dirty page scope to be limited to pinned pages? > There > > > are complications around non-singleton IOMMU groups, but I think > we're > > > already leaning towards that being a non-worthwhile problem to solve. > > > So if we require that only singleton IOMMU groups can pin pages and > we > > > pass the IOMMU group as a parameter to > > > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a > > > flag on its local vfio_group struct to indicate dirty page scope is > > > limited to pinned pages. We might want to keep a flag on the > > > vfio_iommu struct to indicate if all of the vfio_groups for each > > > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to > > > pinned pages as an optimization to avoid walking lists too often. Then > > > we could test if vfio_iommu.domain_list is not empty and this new flag > > > does not limit the dirty page scope, then everything within each > > > vfio_dma is considered dirty. > > > > > > > hi Alex > > could you help clarify whether my understandings below are right? > > In future, > > 1. for mdev and for passthrough device withoug hardware ability to track > > dirty pages, the vendor driver has to explicitly call > > vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page > > set. > > For non-IOMMU backed mdevs without hardware dirty page tracking, > there's no change to the vendor driver currently. Pages pinned by the > vendor driver are marked as dirty. What about the vendor driver can figure out, in software means, which pinned pages are actually dirty? In that case, would a separate mark_dirty interface make more sense? Or introduce read/write flag to the pin_pages interface similar to DMA API? Existing drivers always set both r/w flags but just in case then a specific driver may set read-only or write-only... > > For any IOMMU backed device, mdev or direct assignment, all mapped > memory would be considered dirty unless there are explicit calls to pin > pages on top of the IOMMU page pinning and mapping. These would likely > be enabled only when the device is in the _SAVING device_state. > > > 2. for those devices with hardware ability to track dirty pages, will still > > provide a callback to vendor driver to get dirty pages. (as for those > devices, > > it is hard to explicitly call vfio_pin_pages()/vfio_unpin_pages()) > > > > 3. for devices relying on dirty bit info in physical IOMMU, there > > will be a callback to physical IOMMU driver to get dirty page set from > > vfio. > > The proposal here does not cover exactly how these would be > implemented, it only establishes the container as the point of user > interaction with the dirty bitmap and hopefully allows us to maintain > that interface regardless of whether we have dirty tracking at the > device
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, 14 Nov 2019 21:40:35 -0500 Yan Zhao wrote: > On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote: > > On Fri, 15 Nov 2019 00:26:07 +0530 > > Kirti Wankhede wrote: > > > > > On 11/14/2019 1:37 AM, Alex Williamson wrote: > > > > On Thu, 14 Nov 2019 01:07:21 +0530 > > > > Kirti Wankhede wrote: > > > > > > > >> On 11/13/2019 4:00 AM, Alex Williamson wrote: > > > >>> On Tue, 12 Nov 2019 22:33:37 +0530 > > > >>> Kirti Wankhede wrote: > > > >>> > > > All pages pinned by vendor driver through vfio_pin_pages API should > > > be > > > considered as dirty during migration. IOMMU container maintains a > > > list of > > > all such pinned pages. Added an ioctl defination to get bitmap of > > > such > > > >>> > > > >>> definition > > > >>> > > > pinned pages for requested IO virtual address range. > > > >>> > > > >>> Additionally, all mapped pages are considered dirty when physically > > > >>> mapped through to an IOMMU, modulo we discussed devices opting in to > > > >>> per page pinning to indicate finer granularity with a TBD mechanism to > > > >>> figure out if any non-opt-in devices remain. > > > >>> > > > >> > > > >> You mean, in case of device direct assignment (device pass through)? > > > >> > > > > > > > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully > > > > pinned and mapped, then the correct dirty page set is all mapped pages. > > > > We discussed using the vpfn list as a mechanism for vendor drivers to > > > > reduce their migration footprint, but we also discussed that we would > > > > need a way to determine that all participants in the container have > > > > explicitly pinned their working pages or else we must consider the > > > > entire potential working set as dirty. > > > > > > > > > > How can vendor driver tell this capability to iommu module? Any > > > suggestions? > > > > I think it does so by pinning pages. Is it acceptable that if the > > vendor driver pins any pages, then from that point forward we consider > > the IOMMU group dirty page scope to be limited to pinned pages? There > > are complications around non-singleton IOMMU groups, but I think we're > > already leaning towards that being a non-worthwhile problem to solve. > > So if we require that only singleton IOMMU groups can pin pages and we > > pass the IOMMU group as a parameter to > > vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a > > flag on its local vfio_group struct to indicate dirty page scope is > > limited to pinned pages. We might want to keep a flag on the > > vfio_iommu struct to indicate if all of the vfio_groups for each > > vfio_domain in the vfio_iommu.domain_list dirty page scope limited to > > pinned pages as an optimization to avoid walking lists too often. Then > > we could test if vfio_iommu.domain_list is not empty and this new flag > > does not limit the dirty page scope, then everything within each > > vfio_dma is considered dirty. > > > > hi Alex > could you help clarify whether my understandings below are right? > In future, > 1. for mdev and for passthrough device withoug hardware ability to track > dirty pages, the vendor driver has to explicitly call > vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page set. For non-IOMMU backed mdevs without hardware dirty page tracking, there's no change to the vendor driver currently. Pages pinned by the vendor driver are marked as dirty. For any IOMMU backed device, mdev or direct assignment, all mapped memory would be considered dirty unless there are explicit calls to pin pages on top of the IOMMU page pinning and mapping. These would likely be enabled only when the device is in the _SAVING device_state. > 2. for those devices with hardware ability to track dirty pages, will still > provide a callback to vendor driver to get dirty pages. (as for those devices, > it is hard to explicitly call vfio_pin_pages()/vfio_unpin_pages()) > > 3. for devices relying on dirty bit info in physical IOMMU, there > will be a callback to physical IOMMU driver to get dirty page set from > vfio. The proposal here does not cover exactly how these would be implemented, it only establishes the container as the point of user interaction with the dirty bitmap and hopefully allows us to maintain that interface regardless of whether we have dirty tracking at the device or the system IOMMU. Ideally devices with dirty tracking would make use of page pinning and we'd extend the interface to allow vendor drivers the ability to indicate the clean/dirty state of those pinned pages. For system IOMMU dirty page tracking, that potentially might mean that we support IOMMU page faults and the container manages those faults such that the container is the central record of dirty pages. Until these interfaces are designed, we can only speculate, but the goal is to design a user interface compatible with how
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Fri, Nov 15, 2019 at 05:06:25AM +0800, Alex Williamson wrote:
> On Fri, 15 Nov 2019 00:26:07 +0530
> Kirti Wankhede wrote:
>
> > On 11/14/2019 1:37 AM, Alex Williamson wrote:
> > > On Thu, 14 Nov 2019 01:07:21 +0530
> > > Kirti Wankhede wrote:
> > >
> > >> On 11/13/2019 4:00 AM, Alex Williamson wrote:
> > >>> On Tue, 12 Nov 2019 22:33:37 +0530
> > >>> Kirti Wankhede wrote:
> > >>>
> > All pages pinned by vendor driver through vfio_pin_pages API should be
> > considered as dirty during migration. IOMMU container maintains a list
> > of
> > all such pinned pages. Added an ioctl defination to get bitmap of such
> >
> > >>>
> > >>> definition
> > >>>
> > pinned pages for requested IO virtual address range.
> > >>>
> > >>> Additionally, all mapped pages are considered dirty when physically
> > >>> mapped through to an IOMMU, modulo we discussed devices opting in to
> > >>> per page pinning to indicate finer granularity with a TBD mechanism to
> > >>> figure out if any non-opt-in devices remain.
> > >>>
> > >>
> > >> You mean, in case of device direct assignment (device pass through)?
> > >
> > > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
> > > pinned and mapped, then the correct dirty page set is all mapped pages.
> > > We discussed using the vpfn list as a mechanism for vendor drivers to
> > > reduce their migration footprint, but we also discussed that we would
> > > need a way to determine that all participants in the container have
> > > explicitly pinned their working pages or else we must consider the
> > > entire potential working set as dirty.
> > >
> >
> > How can vendor driver tell this capability to iommu module? Any suggestions?
>
> I think it does so by pinning pages. Is it acceptable that if the
> vendor driver pins any pages, then from that point forward we consider
> the IOMMU group dirty page scope to be limited to pinned pages? There
> are complications around non-singleton IOMMU groups, but I think we're
> already leaning towards that being a non-worthwhile problem to solve.
> So if we require that only singleton IOMMU groups can pin pages and we
> pass the IOMMU group as a parameter to
> vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a
> flag on its local vfio_group struct to indicate dirty page scope is
> limited to pinned pages. We might want to keep a flag on the
> vfio_iommu struct to indicate if all of the vfio_groups for each
> vfio_domain in the vfio_iommu.domain_list dirty page scope limited to
> pinned pages as an optimization to avoid walking lists too often. Then
> we could test if vfio_iommu.domain_list is not empty and this new flag
> does not limit the dirty page scope, then everything within each
> vfio_dma is considered dirty.
>
hi Alex
could you help clarify whether my understandings below are right?
In future,
1. for mdev and for passthrough device withoug hardware ability to track
dirty pages, the vendor driver has to explicitly call
vfio_pin_pages()/vfio_unpin_pages() + a flag to tell vfio its dirty page set.
2. for those devices with hardware ability to track dirty pages, will still
provide a callback to vendor driver to get dirty pages. (as for those devices,
it is hard to explicitly call vfio_pin_pages()/vfio_unpin_pages())
3. for devices relying on dirty bit info in physical IOMMU, there
will be a callback to physical IOMMU driver to get dirty page set from
vfio.
Thanks
Yan
> > Signed-off-by: Kirti Wankhede
> > Reviewed-by: Neo Jia
> > ---
> > include/uapi/linux/vfio.h | 23 +++
> > 1 file changed, 23 insertions(+)
> >
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 35b09427ad9f..6fd3822aa610 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> > #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> > #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
> >
> > +/**
> > + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> > + * struct
> > vfio_iommu_type1_dirty_bitmap)
> > + *
> > + * IOCTL to get dirty pages bitmap for IOMMU container during
> > migration.
> > + * Get dirty pages bitmap of given IO virtual addresses range using
> > + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is
> > size of
> > + * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory
> > to get
> > + * bitmap and should set size of allocated memory in bitmap_size
> > field.
> > + * One bit is used to represent per page consecutively starting from
> > iova
> > + * offset. Bit set indicates page at that offset from iova is dirty.
> > + */
> > +struct
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Fri, 15 Nov 2019 00:26:07 +0530
Kirti Wankhede wrote:
> On 11/14/2019 1:37 AM, Alex Williamson wrote:
> > On Thu, 14 Nov 2019 01:07:21 +0530
> > Kirti Wankhede wrote:
> >
> >> On 11/13/2019 4:00 AM, Alex Williamson wrote:
> >>> On Tue, 12 Nov 2019 22:33:37 +0530
> >>> Kirti Wankhede wrote:
> >>>
> All pages pinned by vendor driver through vfio_pin_pages API should be
> considered as dirty during migration. IOMMU container maintains a list of
> all such pinned pages. Added an ioctl defination to get bitmap of such
> >>>
> >>> definition
> >>>
> pinned pages for requested IO virtual address range.
> >>>
> >>> Additionally, all mapped pages are considered dirty when physically
> >>> mapped through to an IOMMU, modulo we discussed devices opting in to
> >>> per page pinning to indicate finer granularity with a TBD mechanism to
> >>> figure out if any non-opt-in devices remain.
> >>>
> >>
> >> You mean, in case of device direct assignment (device pass through)?
> >
> > Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
> > pinned and mapped, then the correct dirty page set is all mapped pages.
> > We discussed using the vpfn list as a mechanism for vendor drivers to
> > reduce their migration footprint, but we also discussed that we would
> > need a way to determine that all participants in the container have
> > explicitly pinned their working pages or else we must consider the
> > entire potential working set as dirty.
> >
>
> How can vendor driver tell this capability to iommu module? Any suggestions?
I think it does so by pinning pages. Is it acceptable that if the
vendor driver pins any pages, then from that point forward we consider
the IOMMU group dirty page scope to be limited to pinned pages? There
are complications around non-singleton IOMMU groups, but I think we're
already leaning towards that being a non-worthwhile problem to solve.
So if we require that only singleton IOMMU groups can pin pages and we
pass the IOMMU group as a parameter to
vfio_iommu_driver_ops.pin_pages(), then the type1 backend can set a
flag on its local vfio_group struct to indicate dirty page scope is
limited to pinned pages. We might want to keep a flag on the
vfio_iommu struct to indicate if all of the vfio_groups for each
vfio_domain in the vfio_iommu.domain_list dirty page scope limited to
pinned pages as an optimization to avoid walking lists too often. Then
we could test if vfio_iommu.domain_list is not empty and this new flag
does not limit the dirty page scope, then everything within each
vfio_dma is considered dirty.
> Signed-off-by: Kirti Wankhede
> Reviewed-by: Neo Jia
> ---
> include/uapi/linux/vfio.h | 23 +++
> 1 file changed, 23 insertions(+)
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 35b09427ad9f..6fd3822aa610 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> #define VFIO_IOMMU_DISABLE_IO(VFIO_TYPE, VFIO_BASE + 16)
>
> +/**
> + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> + * struct
> vfio_iommu_type1_dirty_bitmap)
> + *
> + * IOCTL to get dirty pages bitmap for IOMMU container during migration.
> + * Get dirty pages bitmap of given IO virtual addresses range using
> + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is
> size of
> + * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to
> get
> + * bitmap and should set size of allocated memory in bitmap_size field.
> + * One bit is used to represent per page consecutively starting from
> iova
> + * offset. Bit set indicates page at that offset from iova is dirty.
> + */
> +struct vfio_iommu_type1_dirty_bitmap {
> +__u32argsz;
> +__u32flags;
> +__u64iova; /* IO virtual address */
> +__u64size; /* Size of iova range */
> +__u64bitmap_size; /* in bytes */
> >>>
> >>> This seems redundant. We can calculate the size of the bitmap based on
> >>> the iova size.
> >>>
> >>
> >> But in kernel space, we need to validate the size of memory allocated by
> >> user instead of assuming user is always correct, right?
> >
> > What does it buy us for the user to tell us the size? They could be
> > wrong, they could be malicious. The argsz field on the ioctl is mostly
> > for the handshake that the user is competent, we should get faults from
> > the copy-user operation if it's incorrect.
> >
>
> It is to mainly fail safe.
>
> +void
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On 11/14/2019 1:37 AM, Alex Williamson wrote:
On Thu, 14 Nov 2019 01:07:21 +0530
Kirti Wankhede wrote:
On 11/13/2019 4:00 AM, Alex Williamson wrote:
On Tue, 12 Nov 2019 22:33:37 +0530
Kirti Wankhede wrote:
All pages pinned by vendor driver through vfio_pin_pages API should be
considered as dirty during migration. IOMMU container maintains a list of
all such pinned pages. Added an ioctl defination to get bitmap of such
definition
pinned pages for requested IO virtual address range.
Additionally, all mapped pages are considered dirty when physically
mapped through to an IOMMU, modulo we discussed devices opting in to
per page pinning to indicate finer granularity with a TBD mechanism to
figure out if any non-opt-in devices remain.
You mean, in case of device direct assignment (device pass through)?
Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
pinned and mapped, then the correct dirty page set is all mapped pages.
We discussed using the vpfn list as a mechanism for vendor drivers to
reduce their migration footprint, but we also discussed that we would
need a way to determine that all participants in the container have
explicitly pinned their working pages or else we must consider the
entire potential working set as dirty.
How can vendor driver tell this capability to iommu module? Any suggestions?
Signed-off-by: Kirti Wankhede
Reviewed-by: Neo Jia
---
include/uapi/linux/vfio.h | 23 +++
1 file changed, 23 insertions(+)
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 35b09427ad9f..6fd3822aa610 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
#define VFIO_IOMMU_ENABLE_IO(VFIO_TYPE, VFIO_BASE + 15)
#define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
+/**
+ * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
+ * struct vfio_iommu_type1_dirty_bitmap)
+ *
+ * IOCTL to get dirty pages bitmap for IOMMU container during migration.
+ * Get dirty pages bitmap of given IO virtual addresses range using
+ * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is size of
+ * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to get
+ * bitmap and should set size of allocated memory in bitmap_size field.
+ * One bit is used to represent per page consecutively starting from iova
+ * offset. Bit set indicates page at that offset from iova is dirty.
+ */
+struct vfio_iommu_type1_dirty_bitmap {
+ __u32argsz;
+ __u32flags;
+ __u64iova; /* IO virtual address */
+ __u64size; /* Size of iova range */
+ __u64bitmap_size; /* in bytes */
This seems redundant. We can calculate the size of the bitmap based on
the iova size.
But in kernel space, we need to validate the size of memory allocated by
user instead of assuming user is always correct, right?
What does it buy us for the user to tell us the size? They could be
wrong, they could be malicious. The argsz field on the ioctl is mostly
for the handshake that the user is competent, we should get faults from
the copy-user operation if it's incorrect.
It is to mainly fail safe.
+ void __user *bitmap;/* one bit per page */
Should we define that as a __u64* to (a) help with the size
calculation, and (b) assure that we can use 8-byte ops on it?
However, who defines page size? Is it necessarily the processor page
size? A physical IOMMU may support page sizes other than the CPU page
size. It might be more important to indicate the expected page size
than the bitmap size. Thanks,
I see in QEMU and in vfio_iommu_type1 module, page sizes considered for
mapping are CPU page size, 4K. Do we still need to have such argument?
That assumption exists for backwards compatibility prior to supporting
the iova_pgsizes field in vfio_iommu_type1_info. AFAIK the current
interface has no page size assumptions and we should not add any.
So userspace has iova_pgsizes information, which can be input to this
ioctl. Bitmap should be considering smallest page size. Does that makes
sense?
Thanks,
Kirti
Thanks,
Alex
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Thu, 14 Nov 2019 01:07:21 +0530
Kirti Wankhede wrote:
> On 11/13/2019 4:00 AM, Alex Williamson wrote:
> > On Tue, 12 Nov 2019 22:33:37 +0530
> > Kirti Wankhede wrote:
> >
> >> All pages pinned by vendor driver through vfio_pin_pages API should be
> >> considered as dirty during migration. IOMMU container maintains a list of
> >> all such pinned pages. Added an ioctl defination to get bitmap of such
> >
> > definition
> >
> >> pinned pages for requested IO virtual address range.
> >
> > Additionally, all mapped pages are considered dirty when physically
> > mapped through to an IOMMU, modulo we discussed devices opting in to
> > per page pinning to indicate finer granularity with a TBD mechanism to
> > figure out if any non-opt-in devices remain.
> >
>
> You mean, in case of device direct assignment (device pass through)?
Yes, or IOMMU backed mdevs. If vfio_dmas in the container are fully
pinned and mapped, then the correct dirty page set is all mapped pages.
We discussed using the vpfn list as a mechanism for vendor drivers to
reduce their migration footprint, but we also discussed that we would
need a way to determine that all participants in the container have
explicitly pinned their working pages or else we must consider the
entire potential working set as dirty.
> >> Signed-off-by: Kirti Wankhede
> >> Reviewed-by: Neo Jia
> >> ---
> >> include/uapi/linux/vfio.h | 23 +++
> >> 1 file changed, 23 insertions(+)
> >>
> >> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> >> index 35b09427ad9f..6fd3822aa610 100644
> >> --- a/include/uapi/linux/vfio.h
> >> +++ b/include/uapi/linux/vfio.h
> >> @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> >> #define VFIO_IOMMU_ENABLE_IO(VFIO_TYPE, VFIO_BASE + 15)
> >> #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
> >>
> >> +/**
> >> + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> >> + * struct
> >> vfio_iommu_type1_dirty_bitmap)
> >> + *
> >> + * IOCTL to get dirty pages bitmap for IOMMU container during migration.
> >> + * Get dirty pages bitmap of given IO virtual addresses range using
> >> + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is size
> >> of
> >> + * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to
> >> get
> >> + * bitmap and should set size of allocated memory in bitmap_size field.
> >> + * One bit is used to represent per page consecutively starting from iova
> >> + * offset. Bit set indicates page at that offset from iova is dirty.
> >> + */
> >> +struct vfio_iommu_type1_dirty_bitmap {
> >> + __u32argsz;
> >> + __u32flags;
> >> + __u64iova; /* IO virtual address */
> >> + __u64size; /* Size of iova range */
> >> + __u64bitmap_size; /* in bytes */
> >
> > This seems redundant. We can calculate the size of the bitmap based on
> > the iova size.
> >
>
> But in kernel space, we need to validate the size of memory allocated by
> user instead of assuming user is always correct, right?
What does it buy us for the user to tell us the size? They could be
wrong, they could be malicious. The argsz field on the ioctl is mostly
for the handshake that the user is competent, we should get faults from
the copy-user operation if it's incorrect.
> >> + void __user *bitmap;/* one bit per page */
> >
> > Should we define that as a __u64* to (a) help with the size
> > calculation, and (b) assure that we can use 8-byte ops on it?
> >
> > However, who defines page size? Is it necessarily the processor page
> > size? A physical IOMMU may support page sizes other than the CPU page
> > size. It might be more important to indicate the expected page size
> > than the bitmap size. Thanks,
> >
>
> I see in QEMU and in vfio_iommu_type1 module, page sizes considered for
> mapping are CPU page size, 4K. Do we still need to have such argument?
That assumption exists for backwards compatibility prior to supporting
the iova_pgsizes field in vfio_iommu_type1_info. AFAIK the current
interface has no page size assumptions and we should not add any.
Thanks,
Alex
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On 11/13/2019 4:00 AM, Alex Williamson wrote:
On Tue, 12 Nov 2019 22:33:37 +0530
Kirti Wankhede wrote:
All pages pinned by vendor driver through vfio_pin_pages API should be
considered as dirty during migration. IOMMU container maintains a list of
all such pinned pages. Added an ioctl defination to get bitmap of such
definition
pinned pages for requested IO virtual address range.
Additionally, all mapped pages are considered dirty when physically
mapped through to an IOMMU, modulo we discussed devices opting in to
per page pinning to indicate finer granularity with a TBD mechanism to
figure out if any non-opt-in devices remain.
You mean, in case of device direct assignment (device pass through)?
Signed-off-by: Kirti Wankhede
Reviewed-by: Neo Jia
---
include/uapi/linux/vfio.h | 23 +++
1 file changed, 23 insertions(+)
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 35b09427ad9f..6fd3822aa610 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
#define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
#define VFIO_IOMMU_DISABLE_IO(VFIO_TYPE, VFIO_BASE + 16)
+/**
+ * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
+ * struct vfio_iommu_type1_dirty_bitmap)
+ *
+ * IOCTL to get dirty pages bitmap for IOMMU container during migration.
+ * Get dirty pages bitmap of given IO virtual addresses range using
+ * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is size of
+ * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to get
+ * bitmap and should set size of allocated memory in bitmap_size field.
+ * One bit is used to represent per page consecutively starting from iova
+ * offset. Bit set indicates page at that offset from iova is dirty.
+ */
+struct vfio_iommu_type1_dirty_bitmap {
+ __u32argsz;
+ __u32flags;
+ __u64iova; /* IO virtual address */
+ __u64size; /* Size of iova range */
+ __u64bitmap_size; /* in bytes */
This seems redundant. We can calculate the size of the bitmap based on
the iova size.
But in kernel space, we need to validate the size of memory allocated by
user instead of assuming user is always correct, right?
+ void __user *bitmap;/* one bit per page */
Should we define that as a __u64* to (a) help with the size
calculation, and (b) assure that we can use 8-byte ops on it?
However, who defines page size? Is it necessarily the processor page
size? A physical IOMMU may support page sizes other than the CPU page
size. It might be more important to indicate the expected page size
than the bitmap size. Thanks,
I see in QEMU and in vfio_iommu_type1 module, page sizes considered for
mapping are CPU page size, 4K. Do we still need to have such argument?
Thanks,
Kirti
Alex
+};
+
+#define VFIO_IOMMU_GET_DIRTY_BITMAP _IO(VFIO_TYPE, VFIO_BASE + 17)
+
/* Additional API for SPAPR TCE (Server POWERPC) IOMMU */
/*
Re: [PATCH v9 Kernel 2/5] vfio iommu: Add ioctl defination to get dirty pages bitmap.
On Tue, 12 Nov 2019 22:33:37 +0530
Kirti Wankhede wrote:
> All pages pinned by vendor driver through vfio_pin_pages API should be
> considered as dirty during migration. IOMMU container maintains a list of
> all such pinned pages. Added an ioctl defination to get bitmap of such
definition
> pinned pages for requested IO virtual address range.
Additionally, all mapped pages are considered dirty when physically
mapped through to an IOMMU, modulo we discussed devices opting in to
per page pinning to indicate finer granularity with a TBD mechanism to
figure out if any non-opt-in devices remain.
> Signed-off-by: Kirti Wankhede
> Reviewed-by: Neo Jia
> ---
> include/uapi/linux/vfio.h | 23 +++
> 1 file changed, 23 insertions(+)
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 35b09427ad9f..6fd3822aa610 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -902,6 +902,29 @@ struct vfio_iommu_type1_dma_unmap {
> #define VFIO_IOMMU_ENABLE_IO(VFIO_TYPE, VFIO_BASE + 15)
> #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
>
> +/**
> + * VFIO_IOMMU_GET_DIRTY_BITMAP - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> + * struct vfio_iommu_type1_dirty_bitmap)
> + *
> + * IOCTL to get dirty pages bitmap for IOMMU container during migration.
> + * Get dirty pages bitmap of given IO virtual addresses range using
> + * struct vfio_iommu_type1_dirty_bitmap. Caller sets argsz, which is size of
> + * struct vfio_iommu_type1_dirty_bitmap. User should allocate memory to get
> + * bitmap and should set size of allocated memory in bitmap_size field.
> + * One bit is used to represent per page consecutively starting from iova
> + * offset. Bit set indicates page at that offset from iova is dirty.
> + */
> +struct vfio_iommu_type1_dirty_bitmap {
> + __u32argsz;
> + __u32flags;
> + __u64iova; /* IO virtual address */
> + __u64size; /* Size of iova range */
> + __u64bitmap_size; /* in bytes */
This seems redundant. We can calculate the size of the bitmap based on
the iova size.
> + void __user *bitmap;/* one bit per page */
Should we define that as a __u64* to (a) help with the size
calculation, and (b) assure that we can use 8-byte ops on it?
However, who defines page size? Is it necessarily the processor page
size? A physical IOMMU may support page sizes other than the CPU page
size. It might be more important to indicate the expected page size
than the bitmap size. Thanks,
Alex
> +};
> +
> +#define VFIO_IOMMU_GET_DIRTY_BITMAP _IO(VFIO_TYPE, VFIO_BASE +
> 17)
> +
> /* Additional API for SPAPR TCE (Server POWERPC) IOMMU */
>
> /*
