Re: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
On 09/12/2014 03:49, Tian, Kevin wrote: - Now we have XenGT/KVMGT separately maintained, and KVMGT lags behind XenGT regarding to features and qualities. Likely you'll continue see stale code (like Xen inst decoder) for some time. In the future we plan to maintain a single kernel repo for both, so KVMGT can share same quality as XenGT once KVM in-kernel dm framework is stable. - Regarding to Qemu hacks, KVMGT really doesn't have any different requirements as what have been discussed for GPU pass-through, e.g. about ISA bridge. Our implementation is based on an old Qemu repo, and honestly speaking not cleanly developed, because we know we can leverage from GPU pass-through support once it's in Qemu. At that time we'll leverage the same logic with minimal changes to hook KVMGT mgmt. APIs (e.g. create/destroy a vGPU instance). So we can ignore this area for now. :-) Could the virtual device model introduce new registers in order to avoid poking at the ISA bridge? I'm not sure that you can leverage from GPU pass-through support once it's in Qemu, since the Xen IGD passthrough support is being added to a separate machine that is specific to Xen IGD passthrough; no ISA bridge hacking will probably be allowed on the -M pc and -M q35 machine types. Paolo -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
From: Paolo Bonzini [mailto:pbonz...@redhat.com] Sent: Thursday, December 11, 2014 12:59 AM On 09/12/2014 03:49, Tian, Kevin wrote: - Now we have XenGT/KVMGT separately maintained, and KVMGT lags behind XenGT regarding to features and qualities. Likely you'll continue see stale code (like Xen inst decoder) for some time. In the future we plan to maintain a single kernel repo for both, so KVMGT can share same quality as XenGT once KVM in-kernel dm framework is stable. - Regarding to Qemu hacks, KVMGT really doesn't have any different requirements as what have been discussed for GPU pass-through, e.g. about ISA bridge. Our implementation is based on an old Qemu repo, and honestly speaking not cleanly developed, because we know we can leverage from GPU pass-through support once it's in Qemu. At that time we'll leverage the same logic with minimal changes to hook KVMGT mgmt. APIs (e.g. create/destroy a vGPU instance). So we can ignore this area for now. :-) Could the virtual device model introduce new registers in order to avoid poking at the ISA bridge? I'm not sure that you can leverage from GPU pass-through support once it's in Qemu, since the Xen IGD passthrough support is being added to a separate machine that is specific to Xen IGD passthrough; no ISA bridge hacking will probably be allowed on the -M pc and -M q35 machine types. My point is that KVMGT doesn't introduce new requirements as what's required in IGD passthrough case, because all the hacks you see now is to satisfy guest graphics driver's expectation. I haven't follow up the KVM IGD passthrough progress, but if it doesn't require ISA bridge hacking the same trick can be adopted by KVMGT too. You may know Allen is working on driver changes to avoid causing those hacks in Qemu side. That effort will benefit us too. So I don't think this is a KVMGT specific issue, and we need a common solution to close this gap instead of hacking vGPU device model alone. Thanks Kevin
Re: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
CC Kevin. On 12/09/2014 05:54 PM, Jan Kiszka wrote: On 2014-12-04 03:24, Jike Song wrote: Hi all, We are pleased to announce the first release of KVMGT project. KVMGT is the implementation of Intel GVT-g technology, a full GPU virtualization solution. Under Intel GVT-g, a virtual GPU instance is maintained for each VM, with part of performance critical resources directly assigned. The capability of running native graphics driver inside a VM, without hypervisor intervention in performance critical paths, achieves a good balance of performance, feature, and sharing capability. KVMGT is still in the early stage: - Basic functions of full GPU virtualization works, guest can see a full-featured vGPU. We ran several 3D workloads such as lightsmark, nexuiz, urbanterror and warsow. - Only Linux guest supported so far, and PPGTT must be disabled in guest through a kernel parameter(see README.kvmgt in QEMU). - This drop also includes some Xen specific changes, which will be cleaned up later. - Our end goal is to upstream both XenGT and KVMGT, which shares ~90% logic for vGPU device model (will be part of i915 driver), with only difference in hypervisor specific services - insufficient test coverage, so please bear with stability issues :) There are things need to be improved, esp. the KVM interfacing part: 1a domid was added to each KVMGT guest An ID is needed for foreground OS switching, e.g. # echo domid/sys/kernel/vgt/control/foreground_vm domid 0 is reserved for host OS. 2SRCU workarounds. Some KVM functions, such as: kvm_io_bus_register_dev install_new_memslots must be called *without* kvm-srcu read-locked. Otherwise it hangs. In KVMGT, we need to register an iodev only *after* BAR registers are written by guest. That means, we already have kvm-srcu hold - trapping/emulating PIO(BAR registers) makes us in such a condition. That will make kvm_io_bus_register_dev hangs. Currently we have to disable rcu_assign_pointer() in such functions. These were dirty workarounds, your suggestions are high welcome! 3syscalls were called to access /dev/mem from kernel An in-kernel memslot was added for aperture, but using syscalls like open and mmap to open and access the character device /dev/mem, for pass-through. The source codes(kernel, qemu as well as seabios) are available at github: git://github.com/01org/KVMGT-kernel git://github.com/01org/KVMGT-qemu git://github.com/01org/KVMGT-seabios In the KVMGT-qemu repository, there is a README.kvmgt to be referred. More information about Intel GVT-g and KVMGT can be found at: https://www.usenix.org/conference/atc14/technical-sessions/presentation/tian http://events.linuxfoundation.org/sites/events/files/slides/KVMGT-a%20Full%20GPU%20Virtualization%20Solution_1.pdf Appreciate your comments, BUG reports, and contributions! There is an even increasing interest to keep KVM's in-kernel guest interface as small as possible, specifically for security reasons. I'm sure there are some good performance reasons to create a new in-kernel device model, but I suppose those will need good evidences why things are done in the way they finally should be - and not via a user-space device model. This is likely not a binary decision (all userspace vs. no userspace), it is more about the size and robustness of the in-kernel model vs. its performance. One aspect could also be important: Are there hardware improvements in sight that will eventually help to reduce the in-kernel device model and make the overall design even more robust? How will those changes fit best into a proposed user/kernel split? Jan -- Thanks, Jike ___ Intel-gfx mailing list intel-...@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
From: Song, Jike Sent: Wednesday, December 10, 2014 2:34 PM CC Kevin. On 12/09/2014 05:54 PM, Jan Kiszka wrote: On 2014-12-04 03:24, Jike Song wrote: Hi all, We are pleased to announce the first release of KVMGT project. KVMGT is the implementation of Intel GVT-g technology, a full GPU virtualization solution. Under Intel GVT-g, a virtual GPU instance is maintained for each VM, with part of performance critical resources directly assigned. The capability of running native graphics driver inside a VM, without hypervisor intervention in performance critical paths, achieves a good balance of performance, feature, and sharing capability. KVMGT is still in the early stage: - Basic functions of full GPU virtualization works, guest can see a full-featured vGPU. We ran several 3D workloads such as lightsmark, nexuiz, urbanterror and warsow. - Only Linux guest supported so far, and PPGTT must be disabled in guest through a kernel parameter(see README.kvmgt in QEMU). - This drop also includes some Xen specific changes, which will be cleaned up later. - Our end goal is to upstream both XenGT and KVMGT, which shares ~90% logic for vGPU device model (will be part of i915 driver), with only difference in hypervisor specific services - insufficient test coverage, so please bear with stability issues :) There are things need to be improved, esp. the KVM interfacing part: 1a domid was added to each KVMGT guest An ID is needed for foreground OS switching, e.g. # echo domid /sys/kernel/vgt/control/foreground_vm domid 0 is reserved for host OS. 2SRCU workarounds. Some KVM functions, such as: kvm_io_bus_register_dev install_new_memslots must be called *without* kvm-srcu read-locked. Otherwise it hangs. In KVMGT, we need to register an iodev only *after* BAR registers are written by guest. That means, we already have kvm-srcu hold - trapping/emulating PIO(BAR registers) makes us in such a condition. That will make kvm_io_bus_register_dev hangs. Currently we have to disable rcu_assign_pointer() in such functions. These were dirty workarounds, your suggestions are high welcome! 3syscalls were called to access /dev/mem from kernel An in-kernel memslot was added for aperture, but using syscalls like open and mmap to open and access the character device /dev/mem, for pass-through. The source codes(kernel, qemu as well as seabios) are available at github: git://github.com/01org/KVMGT-kernel git://github.com/01org/KVMGT-qemu git://github.com/01org/KVMGT-seabios In the KVMGT-qemu repository, there is a README.kvmgt to be referred. More information about Intel GVT-g and KVMGT can be found at: https://www.usenix.org/conference/atc14/technical-sessions/presentation/tia n http://events.linuxfoundation.org/sites/events/files/slides/KVMGT-a%20Full%2 0GPU%20Virtualization%20Solution_1.pdf Appreciate your comments, BUG reports, and contributions! There is an even increasing interest to keep KVM's in-kernel guest interface as small as possible, specifically for security reasons. I'm sure there are some good performance reasons to create a new in-kernel device model, but I suppose those will need good evidences why things are done in the way they finally should be - and not via a user-space device model. This is likely not a binary decision (all userspace vs. no userspace), it is more about the size and robustness of the in-kernel model vs. its performance. Thanks for explaining the background. We're not against the userspace model if applied, but based on our analysis we figured out the in-kernel model is the best suite, not just for performance reason, but also for the tight couple to i915 functionalities (scheduling, interrupt, security, etc.) and hypervisor functionalities (GPU shadow page table, etc.) which are best handled in kernel directly. Definitely we don't want to split it just for performance reason, w/o a functionally clear separation, because that just creates unnecessary/messy user/kernel interfaces. And now we've got i915 community's signal that they're willing to pick the core code into i915 driver, which we're currently working on. So, not to eliminate the possibility of user/kernel split, how about we first look at those in-kernel dm changes for KVM? Then you can help judge whether it's a reasonable change or instead there's a better option. Jike will summarize and start the discussion in a separate thread. One aspect could also be important: Are there hardware improvements in sight that will eventually help to reduce the in-kernel
Re: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
On Mon, Dec 08, 2014 at 10:55:01AM +0100, Gerd Hoffmann wrote: On Sa, 2014-12-06 at 12:17 +0800, Jike Song wrote: I don't know that is exactly needed, we also need to have Windows driver considered. However, I'm quite confident that, if things gonna work for IGD passthrough, it gonna work for GVT-g. I'd suggest to focus on q35 emulation. q35 is new enough that a version with integrated graphics exists, so the gap we have to close is *much* smaller. In case guests expect a northbridge matching the chipset generation of the graphics device (which I'd expect is the case, after digging a bit in the igd and agpgart linux driver code) I think we should add proper device emulation for them, i.e. comply q35-pcihost with sandybridge-pcihost + ivybridge-pcihost + haswell-pcihost instead of just copying over the pci ids from the host. Most likely all those variants can share most of the emulation code. I don't think i915.ko should care about either northbridge nor pch on para-virtualized platforms. We do noodle around in there for the oddball memory controller setting and for some display stuff. But neither of that really applies to paravirtualized hw. And if there's any case like that we should patch it out (like we do with some of the runtime pm code already). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
Here is some background of this KVMGT release: - the major purpose is for early experiment of this technique in KVM, and throw out issues about adding in-kernel device model (or mediated pass-through framework) in KVM. - KVMGT shares 90% code as XenGT, regarding to vGPU device model. The only difference is the in-kernel dm interface. The vGPU device model will be split and integrated in i915 driver. It will register to in-kernel dm framework provided either by Xen or KVM at boot time. Upstreaming of vGPU device model is already in progress, with valuable comments received from i915 community. However the refactoring mostly happen in XenGT repo now - Now we have XenGT/KVMGT separately maintained, and KVMGT lags behind XenGT regarding to features and qualities. Likely you'll continue see stale code (like Xen inst decoder) for some time. In the future we plan to maintain a single kernel repo for both, so KVMGT can share same quality as XenGT once KVM in-kernel dm framework is stable. - Regarding to Qemu hacks, KVMGT really doesn't have any different requirements as what have been discussed for GPU pass-through, e.g. about ISA bridge. Our implementation is based on an old Qemu repo, and honestly speaking not cleanly developed, because we know we can leverage from GPU pass-through support once it's in Qemu. At that time we'll leverage the same logic with minimal changes to hook KVMGT mgmt. APIs (e.g. create/destroy a vGPU instance). So we can ignore this area for now. :-) Thanks Kevin From: Paolo Bonzini Sent: Friday, December 05, 2014 9:04 PM On 05/12/2014 09:50, Gerd Hoffmann wrote: A few comments on the kernel stuff (brief look so far, also compile-tested only, intel gfx on my test machine is too old). * Noticed the kernel bits don't even compile when configured as module. Everything (vgt, i915, kvm) must be compiled into the kernel. I'll add that the patch is basically impossible to review with all the XenGT bits still in. For example, the x86 emulator seems to be unnecessary for KVMGT, but I am not 100% sure. I would like a clear understanding of why/how Andrew Barnes was able to do i915 passthrough (GVT-d) without hacking the ISA bridge, and why this does not apply to GVT-g. Paolo * Design approach still seems to be i915 on vgt not the other way around. Qemu/SeaBIOS bits: I've seen the host bridge changes identity from i440fx to copy-pci-ids-from-host. Guess the reason for this is that seabios uses this device to figure whenever it is running on i440fx or q35. Correct? What are the exact requirements for the device? Must it match the host exactly, to not confuse the guest intel graphics driver? Or would something more recent -- such as the q35 emulation qemu has -- be good enough to make things work (assuming we add support for the graphic-related pci config space registers there)? The patch also adds a dummy isa bridge at 0x1f. Simliar question here: What exactly is needed here? Would things work if we simply use the q35 lpc device here? more to come after I've read the paper linked above ... cheers, Gerd ___ Intel-gfx mailing list intel-...@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx ___ Intel-gfx mailing list intel-...@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
RE: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
From: Daniel Vetter Sent: Monday, December 08, 2014 6:21 PM On Mon, Dec 08, 2014 at 10:55:01AM +0100, Gerd Hoffmann wrote: On Sa, 2014-12-06 at 12:17 +0800, Jike Song wrote: I don't know that is exactly needed, we also need to have Windows driver considered. However, I'm quite confident that, if things gonna work for IGD passthrough, it gonna work for GVT-g. I'd suggest to focus on q35 emulation. q35 is new enough that a version with integrated graphics exists, so the gap we have to close is *much* smaller. In case guests expect a northbridge matching the chipset generation of the graphics device (which I'd expect is the case, after digging a bit in the igd and agpgart linux driver code) I think we should add proper device emulation for them, i.e. comply q35-pcihost with sandybridge-pcihost + ivybridge-pcihost + haswell-pcihost instead of just copying over the pci ids from the host. Most likely all those variants can share most of the emulation code. I don't think i915.ko should care about either northbridge nor pch on para-virtualized platforms. We do noodle around in there for the oddball memory controller setting and for some display stuff. But neither of that really applies to paravirtualized hw. And if there's any case like that we should patch it out (like we do with some of the runtime pm code already). Agree. Now Allen is working on how to avoid those tricky platform stickiness in Windows gfx driver. We should do same thing in Linux part too. Thanks Kevin
Re: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
On Fri, Dec 05, 2014 at 09:50:21AM +0100, Gerd Hoffmann wrote: https://www.usenix.org/conference/atc14/technical-sessions/presentation/tian /me goes read this. A few comments on the kernel stuff (brief look so far, also compile-tested only, intel gfx on my test machine is too old). * Noticed the kernel bits don't even compile when configured as module. Everything (vgt, i915, kvm) must be compiled into the kernel. * Design approach still seems to be i915 on vgt not the other way around. Yeah done a quick read-through of just the i915 bits too, same comment. I guess this is just the first RFC and the redesign we've discussed about already with xengt is in progress somewhere? Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Intel-gfx] [ANNOUNCE][RFC] KVMGT - the implementation of Intel GVT-g(full GPU virtualization) for KVM
On 12/05/2014 09:54 PM, Daniel Vetter wrote: Yeah done a quick read-through of just the i915 bits too, same comment. I guess this is just the first RFC and the redesign we've discussed about already with xengt is in progress somewhere? Yes, it's marching on with Xen now. The KVM implementation is currently not even feature complete - we still have PPGTT missing. Thanks, Daniel -- Thanks, Jike -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
