+#define EXCPT_BENIGN 0
+#define EXCPT_CONTRIBUTORY 1
+#define EXCPT_PF 2
+
+static int exception_class(int vector)
+{
+ switch (vector) {
+ case PF_VECTOR:
+ return EXCPT_PF;
+ case DE_VECTOR:
+ case TS_VECTOR:
+ case NP_VECTOR:
+ case SS_VECTOR:
+ case GP_VECTOR:
+ return EXCPT_CONTRIBUTORY;
+ default:
+ break;
+ }
+ return EXCPT_BENIGN;
+}
+
+static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
+ unsigned nr, bool has_error, u32 error_code)
+{
+ u32 prev_nr;
+ int class1, class2;
+
+ if (!vcpu->arch.exception.pending) {
+ queue:
+ vcpu->arch.exception.pending = true;
+ vcpu->arch.exception.has_error_code = has_error;
+ vcpu->arch.exception.nr = nr;
+ vcpu->arch.exception.error_code = error_code;
+ return;
+ }
+
+ /* to check exception */
+ prev_nr = vcpu->arch.exception.nr;
+ if (prev_nr == DF_VECTOR) {
+ /* triple fault -> shutdown */
+ set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+ return;
+ }
+ class1 = exception_class(prev_nr);
+ class2 = exception_class(nr);
+ if ((class1 == EXCPT_CONTRIBUTORY && class2 == EXCPT_CONTRIBUTORY)
+ || (class1 == EXCPT_PF && class2 != EXCPT_BENIGN)) {
+ /* generate double fault per SDM Table 5-5 */
+ vcpu->arch.exception.pending = true;
+ vcpu->arch.exception.has_error_code = true;
+ vcpu->arch.exception.nr = DF_VECTOR;
+ vcpu->arch.exception.error_code = 0;
+ } else
+ /* replace previous exception with a new one in a hope
+ that instruction re-execution will regenerate lost
+ exception */
+ goto queue;
+}
+