On Fri, Feb 03, 2023, Lai Jiangshan wrote: > On Thu, Feb 2, 2023 at 9:21 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > > This is logically correct, but there's potential (weird) functional change here. > > If this is called with an invalid root, then KVM will invalidate the GVA in all > > roots prior to this patch, but in no roots after this patch. > > > > I _think_ it should be impossible get here with an invalid root. Can you try > > adding a prep patch to assert that the root is valid so that this patch can > > reasonably assert that there's no functional change? > > > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 508074e47bc0..fffd9b610196 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -792,6 +792,8 @@ void kvm_inject_emulated_page_fault(struct kvm_vcpu *vcpu, > > fault_mmu = fault->nested_page_fault ? vcpu->arch.mmu : > > vcpu->arch.walk_mmu; > > > > + WARN_ON_ONCE(!VALID_PAGE(fault_mmu->root.hpa)); > > + > > I've been updating the patches as per your suggestions. > > And I suddenly realized that when fault->nested_page_fault=false > with nested EPT, fault_mmu->root.hpa is always unset. > > fault_mmu->root.hpa is just meaningless when fault_mmu is not > vcpu->arch.mmu. Right, because there's no KVM-managed MMU. > I will add it as one of the reasons for replacing the argument > with KVM_MMU_ROOT_XXX. And maybe call out that when using walk_mmu, the ->invlpg() implementation is NULL, i.e. using CURRENT root is a nop. Thanks!
