Re: [PATCH v3 04/25] KVM: x86/mmu: Add dedicated API to map guest_memfd pfn into TDP MMU

[Yan Zhao <yan.y.zhao@intel.com>]

On Wed, Oct 22, 2025 at 11:12:47AM -0700, Sean Christopherson wrote:
> On Wed, Oct 22, 2025, Yan Zhao wrote:
> > On Tue, Oct 21, 2025 at 09:36:52AM -0700, Sean Christopherson wrote:
> > > On Tue, Oct 21, 2025, Yan Zhao wrote:
> > > > On Thu, Oct 16, 2025 at 05:32:22PM -0700, Sean Christopherson wrote:
> > Is it good if we test is_page_fault_stale()? e.g.,
> No, because it can only get false positives, e.g. if an mmu_notifier invalidation
> on shared, non-guest_memfd memory.  Though a sanity check would be nice to have;
Right. The false positive is annoying.

> I believe we can simply do:
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c5734ca5c17d..440fd8f80397 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -1273,6 +1273,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>         struct kvm_mmu_page *sp;
>         int ret = RET_PF_RETRY;
>  
> +       KVM_MMU_WARN_ON(!root || root->role.invalid);
> +
>         kvm_mmu_hugepage_adjust(vcpu, fault);
>  
>         trace_kvm_mmu_spte_requested(fault);
Ok.