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KVM: x86: nSVM: Set vmcb02.g_pat correctly for nested NPT

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When KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT is disabled and nested NPT is
enabled in vmcb12, copy the (cached and validated) vmcb12 g_pat field to
vmcb02's g_pat, giving L2 its own independent guest PAT register.

When the quirk is enabled (default), or when NPT is enabled but nested NPT
is disabled, copy L1's IA32_PAT MSR to the vmcb02 g_pat field, since L2
shares the IA32_PAT MSR with L1.

When NPT is disabled, the g_pat field is ignored by hardware.

Fixes: 15038e1472 ("KVM: SVM: obey guest PAT")
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260407190343.325299-5-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Jim Mattson 2026-04-07 12:03:27 -07:00 committed by Sean Christopherson
parent 4b83e4ba83
commit 02233c73f8
1 changed files with 7 additions and 3 deletions
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10
arch/x86/kvm/svm/nested.c
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@ -731,9 +731,6 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm)
struct vmcb *vmcb02 = svm->nested.vmcb02.ptr;
struct kvm_vcpu *vcpu = &svm->vcpu;
nested_vmcb02_compute_g_pat(svm);
vmcb_mark_dirty(vmcb02, VMCB_NPT);
/* Load the nested guest state */
if (svm->nested.vmcb12_gpa != svm->nested.last_vmcb12_gpa) {
new_vmcb12 = true;
@ -764,6 +761,13 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm)
vmcb_mark_dirty(vmcb02, VMCB_CET);
}
if (l2_has_separate_pat(vcpu)) {
if (unlikely(new_vmcb12 || vmcb12_is_dirty(control, VMCB_NPT)))
vmcb_set_gpat(vmcb02, svm->nested.save.g_pat);
} else if (npt_enabled) {
vmcb_set_gpat(vmcb02, vcpu->arch.pat);
}
kvm_set_rflags(vcpu, save->rflags | X86_EFLAGS_FIXED);
svm_set_efer(vcpu, svm->nested.save.efer);