Re: [RFC PATCH 3/7] vfio: add spimdev support
On Thu, Aug 02, 2018 at 12:43:27PM -0600, Alex Williamson wrote: > Date: Thu, 2 Aug 2018 12:43:27 -0600 > From: Alex Williamson > To: Cornelia Huck > CC: Kenneth Lee , "Tian, Kevin" > , Kenneth Lee , Jonathan Corbet > , Herbert Xu , "David S . > Miller" , Joerg Roedel , Hao Fang > , Zhou Wang , Zaibo Xu > , Philippe Ombredanne , "Greg > Kroah-Hartman" , Thomas Gleixner > , "linux-...@vger.kernel.org" > , "linux-kernel@vger.kernel.org" > , "linux-cry...@vger.kernel.org" > , "io...@lists.linux-foundation.org" > , "k...@vger.kernel.org" > , "linux-accelerat...@lists.ozlabs.org\" > , Lu Baolu > , Kumar", , " linux...@huawei.com " > "> > Subject: Re: [RFC PATCH 3/7] vfio: add spimdev support > Message-ID: <20180802124327.403b1...@t450s.home> > > On Thu, 2 Aug 2018 10:35:28 +0200 > Cornelia Huck wrote: > > > On Thu, 2 Aug 2018 15:34:40 +0800 > > Kenneth Lee wrote: > > > > > On Thu, Aug 02, 2018 at 04:24:22AM +, Tian, Kevin wrote: > > > > > > > From: Kenneth Lee [mailto:liguo...@hisilicon.com] > > > > > Sent: Thursday, August 2, 2018 11:47 AM > > > > > > > > > > > > > > > > > > From: Kenneth Lee > > > > > > > Sent: Wednesday, August 1, 2018 6:22 PM > > > > > > > > > > > > > > From: Kenneth Lee > > > > > > > > > > > > > > SPIMDEV is "Share Parent IOMMU Mdev". It is a vfio-mdev. But > > > > > > > differ > > > > > from > > > > > > > the general vfio-mdev: > > > > > > > > > > > > > > 1. It shares its parent's IOMMU. > > > > > > > 2. There is no hardware resource attached to the mdev is created. > > > > > > > The > > > > > > > hardware resource (A `queue') is allocated only when the mdev is > > > > > > > opened. > > > > > > > > > > > > Alex has concern on doing so, as pointed out in: > > > > > > > > > > > > https://www.spinics.net/lists/kvm/msg172652.html > > > > > > > > > > > > resource allocation should be reserved at creation time. > > > > > > > > > > Yes. That is why I keep telling that SPIMDEV is not for "VM", it is > > > > > for "many > > > > > processes", it is just an access point to the process. Not a device > > > > > to VM. I > > > > > hope > > > > > Alex can accept it:) > > > > > > > > > > > > > VFIO is just about assigning device resource to user space. It doesn't > > > > care > > > > whether it's native processes or VM using the device so far. Along the > > > > direction > > > > which you described, looks VFIO needs to support the configuration that > > > > some mdevs are used for native process only, while others can be used > > > > for both native and VM. I'm not sure whether there is a clean way to > > > > enforce it... > > > > > > I had the same idea at the beginning. But finally I found that the life > > > cycle > > > of the virtual device for VM and process were different. Consider you > > > create > > > some mdevs for VM use, you will give all those mdevs to lib-virt, which > > > distribute those mdev to VMs or containers. If the VM or container exits, > > > the > > > mdev is returned to the lib-virt and used for next allocation. It is the > > > administrator who controlled every mdev's allocation. > > Libvirt currently does no management of mdev devices, so I believe > this example is fictitious. The extent of libvirt's interaction with > mdev is that XML may specify an mdev UUID as the source for a hostdev > and set the permissions on the device files appropriately. Whether > mdevs are created in advance and re-used or created and destroyed > around a VM instance (for example via qemu hooks scripts) is not a > policy that libvirt imposes. > > > > But for process, it is different. There is no lib-virt in control. The > > > administrator's intension is to grant some type of application to access > > > the > > > hardware. The application can get a handle of the hardware, send request > > > and ge
Re: [RFC PATCH 3/7] vfio: add spimdev support
On Thu, Aug 02, 2018 at 12:43:27PM -0600, Alex Williamson wrote: > Date: Thu, 2 Aug 2018 12:43:27 -0600 > From: Alex Williamson > To: Cornelia Huck > CC: Kenneth Lee , "Tian, Kevin" > , Kenneth Lee , Jonathan Corbet > , Herbert Xu , "David S . > Miller" , Joerg Roedel , Hao Fang > , Zhou Wang , Zaibo Xu > , Philippe Ombredanne , "Greg > Kroah-Hartman" , Thomas Gleixner > , "linux-...@vger.kernel.org" > , "linux-kernel@vger.kernel.org" > , "linux-cry...@vger.kernel.org" > , "io...@lists.linux-foundation.org" > , "k...@vger.kernel.org" > , "linux-accelerat...@lists.ozlabs.org\" > , Lu Baolu > , Kumar", , " linux...@huawei.com " > "> > Subject: Re: [RFC PATCH 3/7] vfio: add spimdev support > Message-ID: <20180802124327.403b1...@t450s.home> > > On Thu, 2 Aug 2018 10:35:28 +0200 > Cornelia Huck wrote: > > > On Thu, 2 Aug 2018 15:34:40 +0800 > > Kenneth Lee wrote: > > > > > On Thu, Aug 02, 2018 at 04:24:22AM +, Tian, Kevin wrote: > > > > > > > From: Kenneth Lee [mailto:liguo...@hisilicon.com] > > > > > Sent: Thursday, August 2, 2018 11:47 AM > > > > > > > > > > > > > > > > > > From: Kenneth Lee > > > > > > > Sent: Wednesday, August 1, 2018 6:22 PM > > > > > > > > > > > > > > From: Kenneth Lee > > > > > > > > > > > > > > SPIMDEV is "Share Parent IOMMU Mdev". It is a vfio-mdev. But > > > > > > > differ > > > > > from > > > > > > > the general vfio-mdev: > > > > > > > > > > > > > > 1. It shares its parent's IOMMU. > > > > > > > 2. There is no hardware resource attached to the mdev is created. > > > > > > > The > > > > > > > hardware resource (A `queue') is allocated only when the mdev is > > > > > > > opened. > > > > > > > > > > > > Alex has concern on doing so, as pointed out in: > > > > > > > > > > > > https://www.spinics.net/lists/kvm/msg172652.html > > > > > > > > > > > > resource allocation should be reserved at creation time. > > > > > > > > > > Yes. That is why I keep telling that SPIMDEV is not for "VM", it is > > > > > for "many > > > > > processes", it is just an access point to the process. Not a device > > > > > to VM. I > > > > > hope > > > > > Alex can accept it:) > > > > > > > > > > > > > VFIO is just about assigning device resource to user space. It doesn't > > > > care > > > > whether it's native processes or VM using the device so far. Along the > > > > direction > > > > which you described, looks VFIO needs to support the configuration that > > > > some mdevs are used for native process only, while others can be used > > > > for both native and VM. I'm not sure whether there is a clean way to > > > > enforce it... > > > > > > I had the same idea at the beginning. But finally I found that the life > > > cycle > > > of the virtual device for VM and process were different. Consider you > > > create > > > some mdevs for VM use, you will give all those mdevs to lib-virt, which > > > distribute those mdev to VMs or containers. If the VM or container exits, > > > the > > > mdev is returned to the lib-virt and used for next allocation. It is the > > > administrator who controlled every mdev's allocation. > > Libvirt currently does no management of mdev devices, so I believe > this example is fictitious. The extent of libvirt's interaction with > mdev is that XML may specify an mdev UUID as the source for a hostdev > and set the permissions on the device files appropriately. Whether > mdevs are created in advance and re-used or created and destroyed > around a VM instance (for example via qemu hooks scripts) is not a > policy that libvirt imposes. > > > > But for process, it is different. There is no lib-virt in control. The > > > administrator's intension is to grant some type of application to access > > > the > > > hardware. The application can get a handle of the hardware, send request > > > and ge
