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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jun 2023 06:41:18.8008 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ec44b2ab-b057-4f9e-e05a-08db6d6b8688 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002529E.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5871 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org SVM/SEV enable debug registers intercepts to skip swapping DRs on entering/exiting the guest. When the guest is in control of debug registers (vcpu->guest_debug == 0), there is an optimisation to reduce the number of context switches: intercepts are cleared and the KVM_DEBUGREG_WONT_EXIT flag is set to tell KVM to do swapping on guest enter/exit. The same code also executes for SEV-ES, however it has no effect as - it always takes (vcpu->guest_debug == 0) branch; - KVM_DEBUGREG_WONT_EXIT is set but DR7 intercept is not cleared; - vcpu_enter_guest() writes DRs but VMRUN for SEV-ES swaps them with the values from _encrypted_ VMSA. Be explicit about SEV-ES not supporting debug: - return right away from dr_interception() and skip unnecessary processing; - return an error right away from the KVM_SEV_LAUNCH_UPDATE_VMSA handler if debugging was already enabled. KVM_SET_GUEST_DEBUG are failing already after KVM_SEV_LAUNCH_UPDATE_VMSA is finished due to vcpu->arch.guest_state_protected set to true. Add WARN_ON to kvm_x86::sync_dirty_debug_regs() (saves guest DRs on guest exit) to signify that SEV-ES won't hit that path. Suggested-by: Sean Christopherson Signed-off-by: Alexey Kardashevskiy --- Changes: v6: * fail in LAUNCH_UPDATE_VMSA instead of clearing the flag * pr_warn_ratelimited -> pr_warn_once * due to the rework, removed Tom's "rb" v5: * new in the series --- arch/x86/kvm/svm/sev.c | 5 +++++ arch/x86/kvm/svm/svm.c | 9 ++++++++- 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 36fe2fcb4698..981286359b72 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -619,6 +619,11 @@ static int __sev_launch_update_vmsa(struct kvm *kvm, struct kvm_vcpu *vcpu, struct vcpu_svm *svm = to_svm(vcpu); int ret; + if (vcpu->guest_debug) { + pr_warn_once("KVM_SET_GUEST_DEBUG for SEV-ES guest is not supported"); + return -EINVAL; + } + /* Perform some pre-encryption checks against the VMSA */ ret = sev_es_sync_vmsa(svm); if (ret) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 9c1b191aed4b..bec6fb82f494 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1996,7 +1996,7 @@ static void svm_sync_dirty_debug_regs(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); - if (vcpu->arch.guest_state_protected) + if (WARN_ON_ONCE(sev_es_guest(vcpu->kvm))) return; get_debugreg(vcpu->arch.db[0], 0); @@ -2727,6 +2727,13 @@ static int dr_interception(struct kvm_vcpu *vcpu) unsigned long val; int err = 0; + /* + * SEV-ES intercepts DR7 only to disable guest debugging and the guest issues a VMGEXIT + * for DR7 write only. KVM cannot change DR7 (always swapped as type 'A') so return early. + */ + if (sev_es_guest(vcpu->kvm)) + return 1; + if (vcpu->guest_debug == 0) { /* * No more DR vmexits; force a reload of the debug registers