[PATCH 6/8] KVM: SVM: Re-inject INTn instead of retrying the insn on "failure"

Sean Christopherson
2022-04-02T01:09:56Z

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>
---
arch/x86/kvm/svm/svm.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ecc828d6921e..00b1399681d1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3425,14 +3425,24 @@ 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;

WARN_ON(!gif_set(svm));

+ 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,
@@ -3787,9 +3797,13 @@ 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)
--
2.35.1.1094.g7c7d902a7c-goog