diff --git a/sys/amd64/vmm/amd/amdvi_hw.c b/sys/amd64/vmm/amd/amdvi_hw.c
--- a/sys/amd64/vmm/amd/amdvi_hw.c
+++ b/sys/amd64/vmm/amd/amdvi_hw.c
@@ -274,6 +274,7 @@
 
 	tail = (struct amdvi_cmd *)((uint8_t *)softc->cmd +
 	    ctrl->cmd_tail);
+	memset(tail, 0, sizeof(*tail));
 
 	return (tail);
 }
@@ -316,7 +317,6 @@
 	uint64_t pa;
 
 	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 
 	pa = vtophys(&softc->cmp_data);
 	cmd->opcode = AMDVI_CMP_WAIT_OPCODE;
@@ -334,7 +334,6 @@
 	struct amdvi_cmd *cmd;
 
 	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 	cmd->opcode = AMDVI_INVD_DTE_OPCODE;
 	cmd->word0 = devid;
 	amdvi_update_cmd_tail(softc);
@@ -352,7 +351,6 @@
 	struct amdvi_cmd *cmd;
 
 	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 
 	cmd->opcode = AMDVI_INVD_PAGE_OPCODE;
 	cmd->word1 = domain_id;
@@ -383,7 +381,6 @@
 		      qlen, RID2PCI_STR(devid));
 	}
 	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 
 #ifdef AMDVI_DEBUG_CMD
 	device_printf(softc->dev, "Invalidate IOTLB devID 0x%x"
@@ -406,7 +403,6 @@
 	struct amdvi_cmd *cmd;
 
 	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 	cmd->opcode = AMDVI_INVD_INTR_OPCODE;
 	cmd->word0 = devid;
 	amdvi_update_cmd_tail(softc);
@@ -420,10 +416,6 @@
 static void
 amdvi_inv_domain(struct amdvi_softc *softc, uint16_t domain_id)
 {
-	struct amdvi_cmd *cmd __diagused;
-
-	cmd = amdvi_get_cmd_tail(softc);
-	KASSERT(cmd != NULL, ("Cmd is NULL"));
 
 	/*
 	 * See section 3.3.3 of IOMMU spec rev 2.0, software note