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.
