[1/2] KVM: SVM: Emulate nRIP feature when reinjecting INT3

Commit Message

Jan Kiszka Feb. 15, 2010, 6:17 p.m. UTC

None

Patch

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 52f78dd..f63f1db 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -46,6 +46,7 @@  MODULE_LICENSE("GPL");
 #define SVM_FEATURE_NPT  (1 << 0)
 #define SVM_FEATURE_LBRV (1 << 1)
 #define SVM_FEATURE_SVML (1 << 2)
+#define SVM_FEATURE_NRIP (1 << 3)
 #define SVM_FEATURE_PAUSE_FILTER (1 << 10)
 
 #define NESTED_EXIT_HOST	0	/* Exit handled on host level */
@@ -109,6 +110,8 @@  struct vcpu_svm {
 	struct nested_state nested;
 
 	bool nmi_singlestep;
+
+	bool int3_injected;
 };
 
 /* enable NPT for AMD64 and X86 with PAE */
@@ -234,23 +237,6 @@  static void svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
 	vcpu->arch.efer = efer;
 }
 
-static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
-				bool has_error_code, u32 error_code)
-{
-	struct vcpu_svm *svm = to_svm(vcpu);
-
-	/* If we are within a nested VM we'd better #VMEXIT and let the
-	   guest handle the exception */
-	if (nested_svm_check_exception(svm, nr, has_error_code, error_code))
-		return;
-
-	svm->vmcb->control.event_inj = nr
-		| SVM_EVTINJ_VALID
-		| (has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
-		| SVM_EVTINJ_TYPE_EXEPT;
-	svm->vmcb->control.event_inj_err = error_code;
-}
-
 static int is_external_interrupt(u32 info)
 {
 	info &= SVM_EVTINJ_TYPE_MASK | SVM_EVTINJ_VALID;
@@ -296,6 +282,36 @@  static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
 	svm_set_interrupt_shadow(vcpu, 0);
 }
 
+static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
+				bool has_error_code, u32 error_code)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	/* If we are within a nested VM we'd better #VMEXIT and let the
+	   guest handle the exception */
+	if (nested_svm_check_exception(svm, nr, has_error_code, error_code))
+		return;
+
+	if (nr == BP_VECTOR && !svm_has(SVM_FEATURE_NRIP)) {
+		/*
+		 * For guest debugging where we have to reinject #BP if some
+		 * INT3 is guest-owned:
+		 * Emulate nRIP by moving RIP one forward. Will fail if
+		 * injection raises a fault that is not intercepted. Still
+		 * better than failing in all cases.
+		 */
+		svm->next_rip = kvm_rip_read(&svm->vcpu) + 1;
+		skip_emulated_instruction(&svm->vcpu);
+		svm->int3_injected = true;
+	}
+
+	svm->vmcb->control.event_inj = nr
+		| SVM_EVTINJ_VALID
+		| (has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
+		| SVM_EVTINJ_TYPE_EXEPT;
+	svm->vmcb->control.event_inj_err = error_code;
+}
+
 static int has_svm(void)
 {
 	const char *msg;
@@ -2653,6 +2669,9 @@  static void svm_complete_interrupts(struct vcpu_svm *svm)
 		if (is_nested(svm))
 			break;
 		if (kvm_exception_is_soft(vector))
+			if (vector == BP_VECTOR && svm->int3_injected)
+				kvm_rip_write(&svm->vcpu,
+					      kvm_rip_read(&svm->vcpu) - 1);
 			break;
 		if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) {
 			u32 err = svm->vmcb->control.exit_int_info_err;
@@ -2667,6 +2686,7 @@  static void svm_complete_interrupts(struct vcpu_svm *svm)
 	default:
 		break;
 	}
+	svm->int3_injected =false;
 }
 
 #ifdef CONFIG_X86_64