kvm: x86: Add payload operands to kvm_multiple_exception

kvm_multiple_exception now takes two additional operands: has_payload
and payload, so that updates to CR2 (and DR6 under VMX) can be delayed
until the exception is delivered. This is necessary to properly
emulate VMX or SVM hardware behavior for nested virtualization.

The new behavior is triggered by
vcpu->kvm->arch.exception_payload_enabled, which will (later) be set
by a new per-VM capability, KVM_CAP_EXCEPTION_PAYLOAD.

Reported-by: Jim Mattson <jmattson@google.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -402,7 +402,7 @@ static int exception_type(int vector)
 
 static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 		unsigned nr, bool has_error, u32 error_code,
-		bool reinject)
+	        bool has_payload, unsigned long payload, bool reinject)
 {
 	u32 prev_nr;
 	int class1, class2;
@@ -424,6 +424,14 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 			 */
 			WARN_ON_ONCE(vcpu->arch.exception.pending);
 			vcpu->arch.exception.injected = true;
+			if (WARN_ON_ONCE(has_payload)) {
+				/*
+				 * A reinjected event has already
+				 * delivered its payload.
+				 */
+				has_payload = false;
+				payload = 0;
+			}
 		} else {
 			vcpu->arch.exception.pending = true;
 			vcpu->arch.exception.injected = false;
@@ -431,8 +439,8 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 		vcpu->arch.exception.has_error_code = has_error;
 		vcpu->arch.exception.nr = nr;
 		vcpu->arch.exception.error_code = error_code;
-		vcpu->arch.exception.has_payload = false;
-		vcpu->arch.exception.payload = 0;
+		vcpu->arch.exception.has_payload = has_payload;
+		vcpu->arch.exception.payload = payload;
 		return;
 	}
 
@@ -468,13 +476,13 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 
 void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr)
 {
-	kvm_multiple_exception(vcpu, nr, false, 0, false);
+	kvm_multiple_exception(vcpu, nr, false, 0, false, 0, false);
 }
 EXPORT_SYMBOL_GPL(kvm_queue_exception);
 
 void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr)
 {
-	kvm_multiple_exception(vcpu, nr, false, 0, true);
+	kvm_multiple_exception(vcpu, nr, false, 0, false, 0, true);
 }
 EXPORT_SYMBOL_GPL(kvm_requeue_exception);
 
@@ -521,13 +529,13 @@ EXPORT_SYMBOL_GPL(kvm_inject_nmi);
 
 void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
 {
-	kvm_multiple_exception(vcpu, nr, true, error_code, false);
+	kvm_multiple_exception(vcpu, nr, true, error_code, false, 0, false);
 }
 EXPORT_SYMBOL_GPL(kvm_queue_exception_e);
 
 void kvm_requeue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
 {
-	kvm_multiple_exception(vcpu, nr, true, error_code, true);
+	kvm_multiple_exception(vcpu, nr, true, error_code, false, 0, true);
 }
 EXPORT_SYMBOL_GPL(kvm_requeue_exception_e);