On Fri, Aug 30, 2024 at 05:15:20PM -0700, Sean Christopherson wrote: > Resume the guest and thus skip emulation of a non-PTE-writing instruction > if and only if unprotecting the gfn actually zapped at least one shadow > page. If the gfn is write-protected for some reason other than shadow > paging, attempting to unprotect the gfn will effectively fail, and thus > retrying the instruction is all but guaranteed to be pointless. This bug > has existed for a long time, but was effectively fudged around by the > retry RIP+address anti-loop detection. > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > --- > arch/x86/kvm/x86.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 966fb301d44b..c4cb6c6d605b 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -8961,14 +8961,14 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt, > if (ctxt->eip == last_retry_eip && last_retry_addr == cr2_or_gpa) > return false; > > + if (!vcpu->arch.mmu->root_role.direct) > + gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2_or_gpa, NULL); > + > + if (!kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa))) > + return false; > + Reviewed-by: Yuan Yao <yuan.yao@xxxxxxxxx> > vcpu->arch.last_retry_eip = ctxt->eip; > vcpu->arch.last_retry_addr = cr2_or_gpa; > - > - if (!vcpu->arch.mmu->root_role.direct) > - gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2_or_gpa, NULL); > - > - kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa)); > - > return true; > } > > -- > 2.46.0.469.g59c65b2a67-goog >
