Index: vmm.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/vmm.c,v
retrieving revision 1.324
diff -u -p -r1.324 vmm.c
--- vmm.c	1 Nov 2022 01:01:14 -0000	1.324
+++ vmm.c	5 Nov 2022 19:25:26 -0000
@@ -116,6 +116,7 @@ SLIST_HEAD(vmlist_head, vm);
  */
 struct vmm_softc {
 	struct device		sc_dev;		/* [r] */
+	unsigned int		sc_open;	/* [K] */
 
 	/* Suspend/Resume Synchronization */
 	struct refcnt		sc_refcnt;
@@ -641,6 +642,10 @@ vmmopen(dev_t dev, int flag, int mode, s
 	if (vmm_softc->mode != VMM_MODE_EPT && vmm_softc->mode != VMM_MODE_RVI)
 		return (ENODEV);
 
+	if (vmm_softc->sc_open)
+		return (EBUSY);
+	vmm_softc->sc_open = 1;
+
 	return 0;
 }
 
@@ -764,6 +769,8 @@ pledge_ioctl_vmm(struct proc *p, long co
 int
 vmmclose(dev_t dev, int flag, int mode, struct proc *p)
 {
+	vmm_softc->sc_open = 0;
+
 	return 0;
 }