Index: sys/dev/iommu/busdma_iommu.c
===================================================================
--- sys/dev/iommu/busdma_iommu.c
+++ sys/dev/iommu/busdma_iommu.c
@@ -974,7 +974,7 @@
 {
 	int error;
 
-	unit->dma_enabled = 1;
+	unit->dma_enabled = 0;
 	error = TUNABLE_INT_FETCH("hw.iommu.dma", &unit->dma_enabled);
 	if (error == 0) /* compatibility */
 		TUNABLE_INT_FETCH("hw.dmar.dma", &unit->dma_enabled);
Index: sys/x86/iommu/intel_drv.c
===================================================================
--- sys/x86/iommu/intel_drv.c
+++ sys/x86/iommu/intel_drv.c
@@ -157,7 +157,7 @@
 	return (1);
 }
 
-static int dmar_enable = 0;
+static int dmar_enable = 1;
 static void
 dmar_identify(driver_t *driver, device_t parent)
 {