From: Jim Mattson Date: Tue, 7 Apr 2026 19:03:31 +0000 (-0700) Subject: KVM: x86: nSVM: Save/restore gPAT with KVM_{GET,SET}_NESTED_STATE X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f256d5770febb9d61f9b57a4c79c491bf4987f1;p=thirdparty%2Fkernel%2Flinux.git KVM: x86: nSVM: Save/restore gPAT with KVM_{GET,SET}_NESTED_STATE Add a 'gpat' field to kvm_svm_nested_state_hdr to carry L2's guest PAT value across save and restore. When KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT is disabled and the vCPU is in guest mode with nested NPT enabled, save vmcb02's g_pat into the header on KVM_GET_NESTED_STATE, and restore it on KVM_SET_NESTED_STATE. Host-initiated accesses to IA32_PAT (via KVM_GET/SET_MSRS) always target L1's hPAT, so they cannot be used to save or restore gPAT. The separate header field ensures that KVM_GET/SET_MSRS and KVM_GET/SET_NESTED_STATE are independent and can be ordered arbitrarily during save and restore. Note that struct kvm_svm_nested_state_hdr is included in a union padded to 120 bytes, so there is room to add the gpat field without changing any offsets. Fixes: cc440cdad5b7 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE") Signed-off-by: Jim Mattson Link: https://patch.msgid.link/20260407190343.325299-9-jmattson@google.com Signed-off-by: Sean Christopherson --- diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 6fa731464aa2..adfb04bbf3db 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -4967,6 +4967,7 @@ Errors: struct kvm_svm_nested_state_hdr { __u64 vmcb_pa; + __u64 gpat; }; struct kvm_vmx_nested_state_data { diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 3ada2fa9ca86..1585ec804066 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -533,6 +533,7 @@ struct kvm_svm_nested_state_data { struct kvm_svm_nested_state_hdr { __u64 vmcb_pa; + __u64 gpat; }; /* for KVM_CAP_NESTED_STATE */ diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 1db821181f43..b326420ac883 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1876,6 +1876,9 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu, /* First fill in the header and copy it out. */ if (is_guest_mode(vcpu)) { kvm_state.hdr.svm.vmcb_pa = svm->nested.vmcb12_gpa; + kvm_state.hdr.svm.gpat = 0; + if (l2_has_separate_pat(vcpu)) + kvm_state.hdr.svm.gpat = svm->vmcb->save.g_pat; kvm_state.size += KVM_STATE_NESTED_SVM_VMCB_SIZE; kvm_state.flags |= KVM_STATE_NESTED_GUEST_MODE; @@ -1928,6 +1931,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, struct vmcb_save_area *save; struct vmcb_save_area_cached save_cached; struct vmcb_ctrl_area_cached ctl_cached; + bool use_separate_l2_pat; unsigned long cr0; int ret; @@ -2004,6 +2008,17 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, !nested_vmcb_check_save(vcpu, &save_cached, false)) goto out_free; + /* + * Validate gPAT when the shared PAT quirk is disabled (i.e. L2 + * has its own gPAT). This is done separately from the + * vmcb_save_area_cached validation above, because gPAT is L2 + * state, but the vmcb_save_area_cached is populated with L1 state. + */ + use_separate_l2_pat = (ctl_cached.misc_ctl & SVM_MISC_ENABLE_NP) && + !kvm_check_has_quirk(vcpu->kvm, + KVM_X86_QUIRK_NESTED_SVM_SHARED_PAT); + if (use_separate_l2_pat && !kvm_pat_valid(kvm_state->hdr.svm.gpat)) + goto out_free; /* * All checks done, we can enter guest mode. Userspace provides @@ -2030,6 +2045,10 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, nested_copy_vmcb_control_to_cache(svm, ctl); svm_switch_vmcb(svm, &svm->nested.vmcb02); + + if (use_separate_l2_pat) + vmcb_set_gpat(svm->vmcb, kvm_state->hdr.svm.gpat); + nested_vmcb02_prepare_control(svm); /*