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

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Date:   Sat,  2 Apr 2022 01:09:01 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Maciej S . Szmigiero" <maciej.szmigiero@...cle.com>
Subject: [PATCH 6/8] 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@...gle.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