When the vCPU is in guest mode with nested NPT enabled, guest accesses to IA32_PAT are redirected to the gPAT register, which is stored in vmcb02->save.g_pat.
Non-guest accesses (e.g. from userspace) to IA32_PAT are always redirected to hPAT, which is stored in vcpu->arch.pat. This is architected behavior. It also makes it possible to restore a new checkpoint on an old kernel with reasonable semantics. After the restore, gPAT will be lost, and L2 will run on L1's PAT. Note that the old kernel would have always run L2 on L1's PAT. Signed-off-by: Jim Mattson <[email protected]> --- arch/x86/kvm/svm/svm.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7041498a8091..3f8581adf0c1 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2846,6 +2846,13 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_AMD64_DE_CFG: msr_info->data = svm->msr_decfg; break; + case MSR_IA32_CR_PAT: + if (!msr_info->host_initiated && is_guest_mode(vcpu) && + nested_npt_enabled(svm)) + msr_info->data = svm->vmcb->save.g_pat; /* gPAT */ + else + msr_info->data = vcpu->arch.pat; /* hPAT */ + break; default: return kvm_get_msr_common(vcpu, msr_info); } @@ -2929,14 +2936,24 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) break; case MSR_IA32_CR_PAT: - ret = kvm_set_msr_common(vcpu, msr); - if (ret) - break; + if (!kvm_pat_valid(data)) + return 1; - svm->vmcb01.ptr->save.g_pat = data; - if (is_guest_mode(vcpu)) - nested_vmcb02_compute_g_pat(svm); - vmcb_mark_dirty(svm->vmcb, VMCB_NPT); + if (!msr->host_initiated && is_guest_mode(vcpu) && + nested_npt_enabled(svm)) { + svm->vmcb->save.g_pat = data; /* gPAT */ + vmcb_mark_dirty(svm->vmcb, VMCB_NPT); + } else { + vcpu->arch.pat = data; /* hPAT */ + if (npt_enabled) { + svm->vmcb01.ptr->save.g_pat = data; + vmcb_mark_dirty(svm->vmcb01.ptr, VMCB_NPT); + if (is_guest_mode(vcpu)) { + svm->vmcb->save.g_pat = data; + vmcb_mark_dirty(svm->vmcb, VMCB_NPT); + } + } + } break; case MSR_IA32_SPEC_CTRL: if (!msr->host_initiated && -- 2.52.0.457.g6b5491de43-goog
