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KVM: x86: nSVM: Clear VMCB_NPT clean bit when updating hPAT from guest mode

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When running an L2 guest and writing to MSR_IA32_CR_PAT, the host PAT value
is stored in both vmcb01's g_pat field and vmcb02's g_pat field, but the
clean bit was only being cleared for vmcb02.

Introduce the helper vmcb_set_gpat() which sets vmcb->save.g_pat and marks
the VMCB dirty for VMCB_NPT. Use this helper in both svm_set_msr() for
updating vmcb01 and in nested_vmcb02_compute_g_pat() for updating vmcb02,
ensuring both VMCBs' NPT fields are properly marked dirty.

Fixes: 4995a3685f ("KVM: SVM: Use a separate vmcb for the nested L2 guest")
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260407190343.325299-3-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Jim Mattson 2026-04-07 12:03:25 -07:00 committed by Sean Christopherson
parent 822790ab01
commit 0a8aeb1584
3 changed files with 8 additions and 3 deletions
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2
arch/x86/kvm/svm/nested.c
View File

@ -701,7 +701,7 @@ void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm)
return;
/* FIXME: merge g_pat from vmcb01 and vmcb12. */
svm->nested.vmcb02.ptr->save.g_pat = svm->vmcb01.ptr->save.g_pat;
vmcb_set_gpat(svm->nested.vmcb02.ptr, svm->vmcb01.ptr->save.g_pat);
}
static bool nested_vmcb12_has_lbrv(struct kvm_vcpu *vcpu)

3
arch/x86/kvm/svm/svm.c
View File

@ -2989,10 +2989,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
if (ret)
break;
svm->vmcb01.ptr->save.g_pat = data;
vmcb_set_gpat(svm->vmcb01.ptr, data);
if (is_guest_mode(vcpu))
nested_vmcb02_compute_g_pat(svm);
vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
break;
case MSR_IA32_SPEC_CTRL:
if (!msr->host_initiated &&

6
arch/x86/kvm/svm/svm.h
View File

@ -465,6 +465,12 @@ static inline bool vmcb12_is_dirty(struct vmcb_ctrl_area_cached *control, int bi
return !test_bit(bit, (unsigned long *)&control->clean);
}
static inline void vmcb_set_gpat(struct vmcb *vmcb, u64 data)
{
vmcb->save.g_pat = data;
vmcb_mark_dirty(vmcb, VMCB_NPT);
}
static __always_inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
{
return container_of(vcpu, struct vcpu_svm, vcpu);