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Message-ID: <5487E96D.70609@intel.com> Date: Wed, 10 Dec 2014 14:34:21 +0800 From: Jike Song <jike.song@...el.com> To: Jan Kiszka <jan.kiszka@...mens.com> CC: kvm@...r.kernel.org, "White, Michael L" <michael.l.white@...el.com>, "Dong, Eddie" <eddie.dong@...el.com>, "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>, "Li, Susie" <susie.li@...el.com>, "Cowperthwaite, David J" <david.j.cowperthwaite@...el.com>, linux-kernel@...r.kernel.org, "Haron, Sandra" <sandra.haron@...el.com>, "Tian, Kevin" <kevin.tian@...el.com> Subject: 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: >> >> 1 a 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. >> >> >> 2 SRCU 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! >> >> >> 3 syscalls 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-gfx@...ts.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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