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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: tOtlcpwwgr96OFWP+RV+NO+dLdLxOGFbqK074NxH+r+DXv/xrb1TAUwcNoZI2t44vGNWdY7/KtqznGIgOJMJ3ZvJroHyg6t03nitFPCndZiHJNefGND6CnlKDikgBC30y0alCll+duV4GpnxpOkqSt9FdOSBGq8bhoPhUM5YZmZKd3/XSZ2OuoAqB0zsVKxvwgungOsAgiZ9SxRs6PJj7A2CcNs5rU8BN4XuCR3K4gffKM/ESgCFH6PBBU5DLF7Ko/UJQ5fX+IyJAKbyxXYHvk2RyrkQyC/1WGs5INvLg9DxCEE8SjrpJ2s9Bva1j4d8/0gezKP25s3k5eCt+Zx18lnGi3kdRtDgvVHor/dnf4/jP8IWGfYcsBulGXl06KjFzaJp4MKsod5DXEX3uy4sYcF7FcSb/wweBvnPJdtyzm0+l7JsaJe+qJkIAfp+GM/9 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Mar 2026 18:21:06.4760 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5d130aa9-72a1-4a49-87fb-08de7e08a15e X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH3PEPF0000000D.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8158 On 07-03-2026 07:44, Sean Christopherson wrote: > On Thu, Jan 29, 2026, Shivansh Dhiman wrote: >> Set the FRED_VIRT_ENABLE bit (bit 4) in the VIRT_EXT field of VMCB to enable >> FRED Virtualization for the guest. This enables automatic save/restore of >> FRED MSRs. Also toggle this bit when setting CPUIDs, to support booting of >> secure guests. >> >> Signed-off-by: Shivansh Dhiman >> --- >> arch/x86/kvm/svm/svm.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >> index 954df4eae90e..24579c149937 100644 >> --- a/arch/x86/kvm/svm/svm.c >> +++ b/arch/x86/kvm/svm/svm.c >> @@ -1144,6 +1144,9 @@ static void init_vmcb(struct kvm_vcpu *vcpu, bool init_event) >> save->fred_ssp3 = 0; >> save->fred_config = 0; >> >> + if (guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) >> + svm->vmcb->control.virt_ext |= FRED_VIRT_ENABLE_MASK; > > This is completely unnecessary, no? CPUID is empty at vCPU creation and so FRED > _can't_ be enabled before going through svm_vcpu_after_set_cpuid(). On a second thought, this is actually redundant. I'll drop this from init_vmcb(). > >> init_sys_seg(&save->ldtr, SEG_TYPE_LDT); >> init_sys_seg(&save->tr, SEG_TYPE_BUSY_TSS16); >> >> @@ -4529,6 +4532,9 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) >> if (guest_cpuid_is_intel_compatible(vcpu)) >> guest_cpu_cap_clear(vcpu, X86_FEATURE_V_VMSAVE_VMLOAD); >> >> + if (guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) >> + svm->vmcb->control.virt_ext |= FRED_VIRT_ENABLE_MASK; > > The flag needs to be cleared if FRED isn't supported, because KVM's wonderful > ABI allows userspace to modify CPUID however many times it wants before running > the vCPU. Agreed. I'll add: if (guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) svm->vmcb->control.virt_ext |= FRED_VIRT_ENABLE_MASK; else svm->vmcb->control.virt_ext &= ~FRED_VIRT_ENABLE_MASK; - Shivansh > >> + >> if (sev_guest(vcpu->kvm)) >> sev_vcpu_after_set_cpuid(svm); >> } >> -- >> 2.43.0 >>