On Mon, Aug 1, 2022 at 6:46 PM Huang, Kai <kai.huang@xxxxxxxxx> wrote: > > > On Mon, Aug 01, 2022, David Matlack wrote: > > > On Thu, May 05, 2022 at 11:14:30AM -0700, isaku.yamahata@xxxxxxxxx wrote: > > > > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > > > > > > > > Explicitly check for an MMIO spte in the fast page fault flow. TDX > > > > will use a not-present entry for MMIO sptes, which can be mistaken > > > > for an access-tracked spte since both have SPTE_SPECIAL_MASK set. > > > > > > > > MMIO sptes are handled in handle_mmio_page_fault for non-TDX VMs, so > > > > this patch does not affect them. TDX will handle MMIO emulation > > > > through a hypercall instead. > > > > > > > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > > > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > > --- > > > > arch/x86/kvm/mmu/mmu.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index > > > > d1c37295bb6e..4a12d862bbb6 100644 > > > > --- a/arch/x86/kvm/mmu/mmu.c > > > > +++ b/arch/x86/kvm/mmu/mmu.c > > > > @@ -3184,7 +3184,7 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, > > struct kvm_page_fault *fault) > > > > else > > > > sptep = fast_pf_get_last_sptep(vcpu, fault->addr, > > &spte); > > > > > > > > - if (!is_shadow_present_pte(spte)) > > > > + if (!is_shadow_present_pte(spte) || is_mmio_spte(spte)) > > > > > > I wonder if this patch is really necessary. is_shadow_present_pte() > > > checks if SPTE_MMU_PRESENT_MASK is set (which is bit 11, not > > > shadow_present_mask). Do TDX VMs set bit 11 in MMIO SPTEs? > > > > This patch should be unnecessary, TDX's not-present SPTEs was one of my > > motivations > > for adding MMU_PRESENT. Bit 11 most definitely must not be set for MMIO > > SPTEs. > > As we already discussed, Isaku will drop this patch. Ah, I missed that discussion. Can you share a link so I can catch up?
