Hi, On to, 2015-08-20 at 17:40 +0800, Zhiyuan Lv wrote: > On Thu, Aug 20, 2015 at 10:22:37AM +0100, Chris Wilson wrote: > > On Thu, Aug 20, 2015 at 04:55:08PM +0800, Zhiyuan Lv wrote: > > > Hi Chris, > > > > > > On Thu, Aug 20, 2015 at 09:34:05AM +0100, Chris Wilson wrote: > > > > On Thu, Aug 20, 2015 at 03:45:20PM +0800, Zhiyuan Lv wrote: > > > > > Broadwell hardware supports both ring buffer mode and > > > > > execlist mode. > > > > > When i915 runs inside a VM with Intel GVT-g, we allow > > > > > execlist mode > > > > > only. The reason is that GVT-g does not support the dynamic > > > > > mode > > > > > switch between ring buffer mode and execlist mode when > > > > > running > > > > > multiple virtual machines. Consider that ring buffer mode is > > > > > legacy > > > > > mode, it makes sense to drop it inside virtual machines. > > > > > > > > If that is the case, you should query the host as to what mode > > > > it is > > > > running. > > > > > > Thanks for the reply! You mean we query the host mode, then tell > > > the > > > guest driver inside VM, so that it could use the same mode as > > > host > > > right? That might be a little complicated, and the only benefit > > > is to > > > support legacy ring buffer mode ... > > > > The only benefit being that the guest works no matter what the host > > does? > > Supporting ring buffer mode may need more work in GVT-g. When we > started to > enable BDW support, ring buffer mode used to work but was not well > tested. And > the inter-VM switch (all in ringbuffer mode) may be tricker comparing > with > driver context switch with "MI_SET_CONTEXT", because we need to > switch ring > buffer whereas driver does not. Regarding this, the EXECLIST mode > looks > cleaner. In order to support that, we may have to: 1, change more LRI > commands > to MMIO in current driver; 2, more testing/debugging of inter-VM > context > switch flow. > > Based on that, I think we should really make statement that "ring > buffer mode" > is not supported by GVT-g on BDW :-) > I think just move the vpgu test even before test for GEN9 just making it return true on intel_vgpu_active(dev) and add a comment that currently vGPU only supports execlist command submission, and then add an error early in the init in some appropriate spot if intel_vgpu_active is true but logical ring context are not available (which would practically mean GEN < 8). Does that sound OK? Regards, Joonas > > -Chris > > _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
