Index: sys/dev/iommu/busdma_iommu.h
===================================================================
--- sys/dev/iommu/busdma_iommu.h
+++ sys/dev/iommu/busdma_iommu.h
@@ -55,6 +55,9 @@
 	bool locked;
 	bool cansleep;
 	int flags;
+#ifdef KMSAN
+	struct memdesc kmsan_mem;
+#endif
 };
 
 #define	BUS_DMAMAP_IOMMU_MALLOC	0x0001
Index: sys/dev/iommu/busdma_iommu.c
===================================================================
--- sys/dev/iommu/busdma_iommu.c
+++ sys/dev/iommu/busdma_iommu.c
@@ -44,6 +44,7 @@
 #include <sys/lock.h>
 #include <sys/proc.h>
 #include <sys/memdesc.h>
+#include <sys/msan.h>
 #include <sys/mutex.h>
 #include <sys/sysctl.h>
 #include <sys/rman.h>
@@ -917,11 +918,28 @@
 }
 
 static void
-iommu_bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map,
+iommu_bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map1,
     bus_dmasync_op_t op)
 {
+	struct bus_dmamap_iommu *map;
+
+	map = (struct bus_dmamap_iommu *)map1;
+	kmsan_bus_dmamap_sync(&map->kmsan_mem, op);
 }
 
+#ifdef KMSAN
+static void
+iommu_bus_dmamap_load_kmsan(bus_dmamap_t map1, struct memdesc *mem)
+{
+	struct bus_dmamap_iommu *map;
+
+	map = (struct bus_dmamap_iommu *)map1;
+	if (map == NULL)
+		return;
+	memcpy(&map->kmsan_mem, mem, sizeof(struct memdesc));
+}
+#endif
+
 struct bus_dma_impl bus_dma_iommu_impl = {
 	.tag_create = iommu_bus_dma_tag_create,
 	.tag_destroy = iommu_bus_dma_tag_destroy,
@@ -938,6 +956,9 @@
 	.map_complete = iommu_bus_dmamap_complete,
 	.map_unload = iommu_bus_dmamap_unload,
 	.map_sync = iommu_bus_dmamap_sync,
+#ifdef KMSAN
+	.load_kmsan = iommu_bus_dmamap_load_kmsan,
+#endif
 };
 
 static void
Index: sys/kern/subr_bus_dma.c
===================================================================
--- sys/kern/subr_bus_dma.c
+++ sys/kern/subr_bus_dma.c
@@ -408,6 +408,11 @@
 	int error;
 	int nsegs;
 
+#ifdef KMSAN
+	mem = memdesc_vaddr(buf, buflen);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	if ((flags & BUS_DMA_NOWAIT) == 0) {
 		mem = memdesc_vaddr(buf, buflen);
 		_bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
@@ -449,6 +454,11 @@
 
 	M_ASSERTPKTHDR(m0);
 
+#ifdef KMSAN
+	struct memdesc mem = memdesc_mbuf(m0);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	flags |= BUS_DMA_NOWAIT;
 	nsegs = -1;
 	error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, NULL, &nsegs, flags);
@@ -471,6 +481,11 @@
 {
 	int error;
 
+#ifdef KMSAN
+	struct memdesc mem = memdesc_mbuf(m0);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	flags |= BUS_DMA_NOWAIT;
 	*nsegs = -1;
 	error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, segs, nsegs, flags);
@@ -486,6 +501,11 @@
 	bus_dma_segment_t *segs;
 	int nsegs, error;
 
+#ifdef KMSAN
+	struct memdesc mem = memdesc_uio(uio);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	flags |= BUS_DMA_NOWAIT;
 	nsegs = -1;
 	error = _bus_dmamap_load_uio(dmat, map, uio, &nsegs, flags);
@@ -513,6 +533,11 @@
 	int error;
 	int nsegs;
 
+#ifdef KMSAN
+	mem = memdesc_ccb(ccb);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	ccb_h = &ccb->ccb_h;
 	if ((ccb_h->flags & CAM_DIR_MASK) == CAM_DIR_NONE) {
 		callback(callback_arg, NULL, 0, 0);
@@ -557,6 +582,11 @@
 	int error;
 	int nsegs;
 
+#ifdef KMSAN
+	mem = memdesc_bio(bio);
+	_bus_dmamap_load_kmsan(dmat, map, &mem);
+#endif
+
 	if ((flags & BUS_DMA_NOWAIT) == 0) {
 		mem = memdesc_bio(bio);
 		_bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
@@ -595,6 +625,10 @@
 	int error;
 	int nsegs;
 
+#ifdef KMSAN
+	_bus_dmamap_load_kmsan(dmat, map, mem);
+#endif
+
 	if ((flags & BUS_DMA_NOWAIT) == 0)
 		_bus_dmamap_waitok(dmat, map, mem, callback, callback_arg);
 
Index: sys/x86/include/bus_dma.h
===================================================================
--- sys/x86/include/bus_dma.h
+++ sys/x86/include/bus_dma.h
@@ -191,4 +191,16 @@
 	return (tc->impl->map_complete(dmat, map, segs, nsegs, error));
 }
 
+#ifdef KMSAN
+static inline void
+_bus_dmamap_load_kmsan(bus_dma_tag_t dmat, bus_dmamap_t map,
+    struct memdesc *mem)
+{
+	struct bus_dma_tag_common *tc;
+
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->load_kmsan(map, mem));
+}
+#endif
+
 #endif /* !_X86_BUS_DMA_H_ */
Index: sys/x86/include/busdma_impl.h
===================================================================
--- sys/x86/include/busdma_impl.h
+++ sys/x86/include/busdma_impl.h
@@ -85,6 +85,9 @@
 	void (*map_unload)(bus_dma_tag_t dmat, bus_dmamap_t map);
 	void (*map_sync)(bus_dma_tag_t dmat, bus_dmamap_t map,
 	    bus_dmasync_op_t op);
+#ifdef KMSAN
+	void (*load_kmsan)(bus_dmamap_t map, struct memdesc *mem);
+#endif
 };
 
 void bus_dma_dflt_lock(void *arg, bus_dma_lock_op_t op);
Index: sys/x86/x86/busdma_bounce.c
===================================================================
--- sys/x86/x86/busdma_bounce.c
+++ sys/x86/x86/busdma_bounce.c
@@ -40,6 +40,7 @@
 #include <sys/lock.h>
 #include <sys/proc.h>
 #include <sys/memdesc.h>
+#include <sys/msan.h>
 #include <sys/mutex.h>
 #include <sys/sysctl.h>
 #include <sys/uio.h>
@@ -66,6 +67,7 @@
 	BUS_DMA_COULD_BOUNCE	= 0x01,
 	BUS_DMA_MIN_ALLOC_COMP	= 0x02,
 	BUS_DMA_KMEM_ALLOC	= 0x04,
+	BUS_DMA_KMSAN		= 0x08,
 };
 
 struct bounce_zone;
@@ -128,6 +130,9 @@
 	bus_dmamap_callback_t *callback;
 	void		      *callback_arg;
 	STAILQ_ENTRY(bus_dmamap) links;
+#ifdef KMSAN
+	struct memdesc	       kmsan_mem;
+#endif
 };
 
 static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
@@ -202,6 +207,10 @@
 	newtag->map_count = 0;
 	newtag->segments = NULL;
 
+#ifdef KMSAN
+	newtag->bounce_flags |= BUS_DMA_KMSAN;
+#endif
+
 	if (parent != NULL && (newtag->common.filter != NULL ||
 	    (parent->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0))
 		newtag->bounce_flags |= BUS_DMA_COULD_BOUNCE;
@@ -361,6 +370,14 @@
 				error = 0;
 		}
 		bz->map_count++;
+	} else if ((dmat->bounce_flags & BUS_DMA_KMSAN) != 0) {
+		/*
+		 * When KMSAN is configured, we need a map to store a memory
+		 * descriptor which can be used for validation.
+		 */
+		*mapp = malloc(sizeof(**mapp), M_DEVBUF, M_NOWAIT | M_ZERO);
+		if (*mapp == NULL)
+			return (ENOMEM);
 	} else {
 		*mapp = NULL;
 	}
@@ -968,7 +985,10 @@
 	vm_offset_t datavaddr, tempvaddr;
 	bus_size_t datacount1, datacount2;
 
-	if (map == NULL || (bpage = STAILQ_FIRST(&map->bpages)) == NULL)
+	if (map == NULL)
+		goto out;
+	kmsan_bus_dmamap_sync(&map->kmsan_mem, op);
+	if ((bpage = STAILQ_FIRST(&map->bpages)) == NULL)
 		goto out;
 
 	/*
@@ -1063,6 +1083,16 @@
 	atomic_thread_fence_rel();
 }
 
+#ifdef KMSAN
+static void
+bounce_bus_dmamap_load_kmsan(bus_dmamap_t map, struct memdesc *mem)
+{
+	if (map == NULL)
+		return;
+	memcpy(&map->kmsan_mem, mem, sizeof(map->kmsan_mem));
+}
+#endif
+
 static void
 init_bounce_pages(void *dummy __unused)
 {
@@ -1344,4 +1374,7 @@
 	.map_complete = bounce_bus_dmamap_complete,
 	.map_unload = bounce_bus_dmamap_unload,
 	.map_sync = bounce_bus_dmamap_sync,
+#ifdef KMSAN
+	.load_kmsan = bounce_bus_dmamap_load_kmsan,
+#endif
 };