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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
