From: Sean Christopherson <seanjc@google.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Farrah Chen <farrah.chen@intel.com>
Subject: Re: [PATCH] KVM: x86: Don't read guest CR3 in async pf flow when guest state is protected
Date: Thu, 11 Dec 2025 08:22:14 -0800 [thread overview]
Message-ID: <aTrvtszjqUFu4Svk@google.com> (raw)
In-Reply-To: <20251211022935.2049039-1-xiaoyao.li@intel.com>
On Thu, Dec 11, 2025, Xiaoyao Li wrote:
> ---
> For AMD SEV-ES and SNP cases, the guest state is also protected. But
> unlike TDX, reading guest CR3 doesn't cause issue since CR3 is always
> marked available for svm vCPUs. It always gets the initial value 0,
> set by kvm_vcpu_reset(). Whether to update vcpu->arch.regs_avail to
> reflect the correct value for SEV-ES and SNP is another topic.
> ---
> arch/x86/kvm/mmu/mmu.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 667d66cf76d5..03be521df6b9 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4521,7 +4521,8 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu,
> arch.gfn = fault->gfn;
> arch.error_code = fault->error_code;
> arch.direct_map = vcpu->arch.mmu->root_role.direct;
> - arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
> + arch.cr3 = vcpu->arch.guest_state_protected ? 0 :
> + kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
>
> return kvm_setup_async_pf(vcpu, fault->addr,
> kvm_vcpu_gfn_to_hva(vcpu, fault->gfn), &arch);
> @@ -4543,7 +4544,8 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> return;
>
> if (!vcpu->arch.mmu->root_role.direct &&
> - work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu))
> + (vcpu->arch.guest_state_protected ||
> + work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu)))
> return;
Protected guests aren't compatible with shadow paging, so I'd rather key off the
direct MMU role. '0' is also a legal address; INVALID_GPA would be better.
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 02c450686b4a..446bf2716d08 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4521,7 +4521,10 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu,
arch.gfn = fault->gfn;
arch.error_code = fault->error_code;
arch.direct_map = vcpu->arch.mmu->root_role.direct;
- arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
+ if (arch.direct_map)
+ arch.cr3 = INVALID_GPA;
+ else
+ arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
return kvm_setup_async_pf(vcpu, fault->addr,
kvm_vcpu_gfn_to_hva(vcpu, fault->gfn), &arch);
prev parent reply other threads:[~2025-12-11 16:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-11 2:29 [PATCH] KVM: x86: Don't read guest CR3 in async pf flow when guest state is protected Xiaoyao Li
2025-12-11 16:22 ` Sean Christopherson [this message]
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