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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Jan 2026 06:38:34.8009 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f3d3b2d1-b661-47bc-01e6-08de5f0106f2 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF00004FBB.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB6971 Content-Type: text/plain; charset="utf-8" From: Neeraj Upadhyay Hardware does not save/restore FRED_RSP0 for Non-SEV-ES guests. Save/restore it early in svm_vcpu_enter_exit() so that the correct physical CPU state is updated. Synchronize the current value of MSR_IA32_FRED_RSP0 in hardware to the kern= el's local cache. Note that the desired host's RSP0 will be set when the CPU exi= ts to userspace for servicing vCPU tasks. Signed-off-by: Neeraj Upadhyay Co-developed-by: Shivansh Dhiman Signed-off-by: Shivansh Dhiman --- arch/x86/kvm/svm/svm.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 05e44e804aba..ddd8941af6f0 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4192,6 +4192,15 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_v= cpu *vcpu, bool spec_ctrl_in { struct svm_cpu_data *sd =3D per_cpu_ptr(&svm_data, vcpu->cpu); struct vcpu_svm *svm =3D to_svm(vcpu); + bool update_fred_rsp0; + + /* + * Hardware does not save/restore FRED_RSP0 for Non-SEV-ES guests. + */ + update_fred_rsp0 =3D !sev_es_guest(vcpu->kvm) && guest_cpu_cap_has(vcpu, = X86_FEATURE_FRED); + + if (update_fred_rsp0) + wrmsrq(MSR_IA32_FRED_RSP0, svm->vmcb->save.fred_rsp0); =20 guest_state_enter_irqoff(); =20 @@ -4218,6 +4227,15 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_v= cpu *vcpu, bool spec_ctrl_in raw_local_irq_disable(); =20 guest_state_exit_irqoff(); + + if (update_fred_rsp0) { + rdmsrq(MSR_IA32_FRED_RSP0, svm->vmcb->save.fred_rsp0); + /* + * Sync hardware MSR value to per-CPU cache. This helps in restoring + * Host RSP0 when exiting to userspace in fred_update_rsp0(). + */ + fred_sync_rsp0(svm->vmcb->save.fred_rsp0); + } } =20 static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_f= lags) --=20 2.43.0