Hi, > > Another area of extension is how to expose a framebuffer to QEMU for > > seamless integration into a SPICE/VNC channel. For this I believe we > > could use a new region, much like we've done to expose VGA access > > through a vfio device file descriptor. An area within this new > > framebuffer region could be directly mappable in QEMU while a > > non-mappable page, at a standard location with standardized format, > > provides a description of framebuffer and potentially even a > > communication channel to synchronize framebuffer captures. This would > > be new code for QEMU, but something we could share among all vGPU > > implementations. > > Now GVT-g already provides an interface to decode framebuffer information, > w/ an assumption that the framebuffer will be further composited into > OpenGL APIs. Can I have a pointer to docs / code? iGVT-g_Setup_Guide.txt mentions a "Indirect Display Mode", but doesn't explain how the guest framebuffer can be accessed then. > So the format is defined according to OpenGL definition. > Does that meet SPICE requirement? Yes and no ;) Some more background: We basically have two rendering paths in qemu. The classic one, without opengl, and a new, still emerging one, using opengl and dma-bufs (gtk support merged for qemu 2.5, sdl2 support will land in 2.6, spice support still WIP, hopefully 2.6 too). For best performance you probably want use the new opengl-based rendering whenever possible. However I do *not* expect the classic rendering path disappear, we'll continue to need that in various cases, most prominent one being vnc support. So, for non-opengl rendering qemu needs the guest framebuffer data so it can feed it into the vnc server. The vfio framebuffer region is meant to support this use case. > Another thing to be added. Framebuffers are frequently switched in > reality. So either Qemu needs to poll or a notification mechanism is required. The idea is to have qemu poll (and adapt poll rate, i.e. without vnc client connected qemu will poll alot less frequently). > And since it's dynamic, having framebuffer page directly exposed in the > new region might be tricky. We can just expose framebuffer information > (including base, format, etc.) and let Qemu to map separately out of VFIO > interface. Allocate some memory, ask gpu to blit the guest framebuffer there, i.e. provide a snapshot of the current guest display instead of playing mapping tricks? > And... this works fine with vGPU model since software knows all the > detail about framebuffer. However in pass-through case, who do you expect > to provide that information? Is it OK to introduce vGPU specific APIs in > VFIO? It will only be used in the vgpu case, not for pass-though. We think it is better to extend the vfio interface to improve vgpu support rather than inventing something new while vfio can satisfy 90% of the vgpu needs already. We want avoid vendor-specific extensions though, the vgpu extension should work across vendors. > Now there is no standard. We expose vGPU life-cycle mgmt. APIs through > sysfs (under i915 node), which is very Intel specific. In reality different > vendors have quite different capabilities for their own vGPUs, so not sure > how standard we can define such a mechanism. Agree when it comes to create vGPU instances. > But this code should be > minor to be maintained in libvirt. As far I know libvirt only needs to discover those devices. If they look like sr/iov devices in sysfs this might work without any changes to libvirt. cheers, Gerd _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
