CC intel-gfx@xxxxxxxxxxxxxxxxxxxxx Thread: https://lore.kernel.org/lkml/a5bb32b8-8bd7-ac98-5c4c-5af604ac8256@xxxxxxxxx/ On Wed, 2022-02-09 at 08:58 -0800, Dave Hansen wrote: > On 1/30/22 13:18, Rick Edgecombe wrote: > > > > diff --git a/drivers/gpu/drm/i915/gvt/gtt.c > > b/drivers/gpu/drm/i915/gvt/gtt.c > > index 99d1781fa5f0..75ce4e823902 100644 > > --- a/drivers/gpu/drm/i915/gvt/gtt.c > > +++ b/drivers/gpu/drm/i915/gvt/gtt.c > > @@ -1210,7 +1210,7 @@ static int split_2MB_gtt_entry(struct > > intel_vgpu *vgpu, > > } > > > > /* Clear dirty field. */ > > - se->val64 &= ~_PAGE_DIRTY; > > + se->val64 &= ~_PAGE_DIRTY_BITS; > > > > ops->clear_pse(se); > > ops->clear_ips(se); > > Are these x86 CPU page table values? I see ->val64 being used like > this: > > e->val64 &= ~GEN8_PAGE_PRESENT; > and > se.val64 |= GEN8_PAGE_PRESENT | GEN8_PAGE_RW; > > where we also have: > > #define GEN8_PAGE_PRESENT BIT_ULL(0) > #define GEN8_PAGE_RW BIT_ULL(1) > > Which tells me that these are probably *close* to the CPU's page > tables. > But, I honestly don't know which format they are. I don't know if > _PAGE_COW is still a software bit in that format or not. > > Either way, I don't think we should be messing with i915 device page > tables. > > Or, are these somehow magically shared with the CPU in some way I > don't > know about? > > [ If these are device-only page tables, it would probably be nice to > stop using _PAGE_FOO for them. It would avoid confusion like this. > ] The two Reviewed-by tags are giving me pause, but as far as I can tell this should not be setting _PAGE_DIRTY_BITS. This code seems to be shadowing guest page tables, and the change would clear the COW software bit in the guest page tables. So, yes, I think this should be dropped.
