Bug fixes.

- Don't enable the HLT intercept by default. It will be enabled by bhyve(8)
  if required. Prior to this change HLT exiting was always enabled making
  the "-H" option to bhyve(8) meaningless.

- Recognize a VM exit triggered by a non-maskable interrupt. Prior to this
  change the exit would be punted to userspace and the virtual machine would
  terminate.

sys/amd64/vmm/amd/svm.c

@@ -503,7 +503,6 @@ vmcb_init(struct svm_softc *sc, int vcpu, uint64_t iopm_base_pa,
 	/* Intercept various events (for e.g. I/O, MSR and CPUID accesses) */
 	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_IO);
 	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_MSR);
-	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_HLT);
 	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_CPUID);
 	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_INTR);
 	svm_enable_intercept(sc, vcpu, VMCB_CTRL1_INTCPT, VMCB_INTCPT_INIT);
@@ -1041,6 +1040,8 @@ exit_reason_to_str(uint64_t reason)
 		return ("mchk");
 	case VMCB_EXIT_INTR:
 		return ("extintr");
+	case VMCB_EXIT_NMI:
+		return ("nmi");
 	case VMCB_EXIT_VINTR:
 		return ("vintr");
 	case VMCB_EXIT_MSR:
@@ -1159,6 +1160,9 @@ svm_vmexit(struct svm_softc *svm_sc, int vcpu, struct vm_exit *vmexit)
 		update_rip = false;
 		vmm_stat_incr(svm_sc->vm, vcpu, VMEXIT_EXTINT, 1);
 		break;
+	case VMCB_EXIT_NMI:
+		update_rip = false;
+		break;
 	case VMCB_EXIT_IO:
 		loop = svm_handle_io(svm_sc, vcpu, vmexit);
 		vmm_stat_incr(svm_sc->vm, vcpu, VMEXIT_INOUT, 1);

sys/amd64/vmm/amd/vmcb.h

@@ -124,6 +124,7 @@
 /* VMCB exit code, APM vol2 Appendix C */
 #define	VMCB_EXIT_MC			0x52
 #define	VMCB_EXIT_INTR			0x60
+#define	VMCB_EXIT_NMI			0x61
 #define	VMCB_EXIT_VINTR			0x64
 #define	VMCB_EXIT_PUSHF			0x70
 #define	VMCB_EXIT_POPF			0x71