KVM: SVM: Re-inject INTn instead of retrying the insn on "failure"

Re-inject INTn software interrupts instead of retrying the instruction if
the CPU encountered an intercepted exception while vectoring the INTn,
e.g. if KVM intercepted a #PF when utilizing shadow paging.  Retrying the
instruction is architecturally wrong e.g. will result in a spurious #DB
if there's a code breakpoint on the INT3/O, and lack of re-injection also
breaks nested virtualization, e.g. if L1 injects a software interrupt and
vectoring the injected interrupt encounters an exception that is
intercepted by L0 but not L1.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <1654ad502f860948e4f2d57b8bd881d67301f785.1651440202.git.maciej.szmigiero@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 525117a49c180ee76b2d7c32172c2af979a8d4b4..0d25dea407965674f3e0bfb2d5b0ba5453e703fd 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -617,10 +617,9 @@ static inline bool is_evtinj_soft(u32 evtinj)
        if (!(evtinj & SVM_EVTINJ_VALID))
                return false;
 
-       /*
-        * Intentionally return false for SOFT events, SVM doesn't yet support
-        * re-injecting soft interrupts.
-        */
+       if (type == SVM_EVTINJ_TYPE_SOFT)
+               return true;
+
        return type == SVM_EVTINJ_TYPE_EXEPT && kvm_exception_is_soft(vector);
 }
 

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ec37647ca068520f51e6a797aa89c00845ae6ace..6248967d4a77cec2ccaf4cc90cc281382800e19e 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3438,12 +3438,22 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
 static void svm_inject_irq(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
+       u32 type;
+
+       if (vcpu->arch.interrupt.soft) {
+               if (svm_update_soft_interrupt_rip(vcpu))
+                       return;
+
+               type = SVM_EVTINJ_TYPE_SOFT;
+       } else {
+               type = SVM_EVTINJ_TYPE_INTR;
+       }
 
        trace_kvm_inj_virq(vcpu->arch.interrupt.nr);
        ++vcpu->stat.irq_injections;
 
        svm->vmcb->control.event_inj = vcpu->arch.interrupt.nr |
-               SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
+                                      SVM_EVTINJ_VALID | type;
 }
 
 void svm_complete_interrupt_delivery(struct kvm_vcpu *vcpu, int delivery_mode,
@@ -3723,6 +3733,8 @@ static inline void sync_lapic_to_cr8(struct kvm_vcpu *vcpu)
 static void svm_complete_soft_interrupt(struct kvm_vcpu *vcpu, u8 vector,
                                        int type)
 {
+       bool is_exception = (type == SVM_EXITINTINFO_TYPE_EXEPT);
+       bool is_soft = (type == SVM_EXITINTINFO_TYPE_SOFT);
        struct vcpu_svm *svm = to_svm(vcpu);
 
        /*
@@ -3734,8 +3746,7 @@ static void svm_complete_soft_interrupt(struct kvm_vcpu *vcpu, u8 vector,
         * the same event, i.e. if the event is a soft exception/interrupt,
         * otherwise next_rip is unused on VMRUN.
         */
-       if (nrips && type == SVM_EXITINTINFO_TYPE_EXEPT &&
-           kvm_exception_is_soft(vector) &&
+       if (nrips && (is_soft || (is_exception && kvm_exception_is_soft(vector))) &&
            kvm_is_linear_rip(vcpu, svm->soft_int_old_rip + svm->soft_int_csbase))
                svm->vmcb->control.next_rip = svm->soft_int_next_rip;
        /*
@@ -3746,7 +3757,7 @@ static void svm_complete_soft_interrupt(struct kvm_vcpu *vcpu, u8 vector,
         * hit a #NP in the guest, and the #NP encountered a #PF, the #NP will
         * be the reported vectored event, but RIP still needs to be unwound.
         */
-       else if (!nrips && type == SVM_EXITINTINFO_TYPE_EXEPT &&
+       else if (!nrips && (is_soft || is_exception) &&
                 kvm_is_linear_rip(vcpu, svm->soft_int_next_rip + svm->soft_int_csbase))
                kvm_rip_write(vcpu, svm->soft_int_old_rip);
 }
@@ -3808,9 +3819,13 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
        case SVM_EXITINTINFO_TYPE_INTR:
                kvm_queue_interrupt(vcpu, vector, false);
                break;
+       case SVM_EXITINTINFO_TYPE_SOFT:
+               kvm_queue_interrupt(vcpu, vector, true);
+               break;
        default:
                break;
        }
+
 }
 
 static void svm_cancel_injection(struct kvm_vcpu *vcpu)