Index: sys/dev/virtio/block/virtio_blk.h
===================================================================
--- sys/dev/virtio/block/virtio_blk.h
+++ sys/dev/virtio/block/virtio_blk.h
@@ -34,16 +34,20 @@
 #define _VIRTIO_BLK_H
 
 /* Feature bits */
-#define VIRTIO_BLK_F_BARRIER	0x0001	/* Does host support barriers? */
-#define VIRTIO_BLK_F_SIZE_MAX	0x0002	/* Indicates maximum segment size */
-#define VIRTIO_BLK_F_SEG_MAX	0x0004	/* Indicates maximum # of segments */
-#define VIRTIO_BLK_F_GEOMETRY	0x0010	/* Legacy geometry available  */
-#define VIRTIO_BLK_F_RO		0x0020	/* Disk is read-only */
-#define VIRTIO_BLK_F_BLK_SIZE	0x0040	/* Block size of disk is available*/
-#define VIRTIO_BLK_F_SCSI	0x0080	/* Supports scsi command passthru */
-#define VIRTIO_BLK_F_WCE	0x0200	/* Writeback mode enabled after reset */
-#define VIRTIO_BLK_F_TOPOLOGY	0x0400	/* Topology information is available */
-#define VIRTIO_BLK_F_CONFIG_WCE 0x0800	/* Writeback mode available in config */
+#define VIRTIO_BLK_F_BARRIER	(1 << 0)	/* Does host support barriers? */
+#define VIRTIO_BLK_F_SIZE_MAX	(1 << 1)	/* Indicates maximum segment size */
+#define VIRTIO_BLK_F_SEG_MAX	(1 << 2)	/* Indicates maximum # of segments */
+#define VIRTIO_BLK_F_GEOMETRY	(1 << 4)	/* Legacy geometry available  */
+#define VIRTIO_BLK_F_RO		(1 << 5)	/* Disk is read-only */
+#define VIRTIO_BLK_F_BLK_SIZE	(1 << 6)	/* Block size of disk is available*/
+#define VIRTIO_BLK_F_SCSI	(1 << 7)	/* Supports scsi command passthru */
+#define VIRTIO_BLK_F_FLUSH	(1 << 9)	/* Writeback mode enabled after reset */
+#define VIRTIO_BLK_F_WCE	(1 << 9)	/* Legacy alias for FLUSH */
+#define VIRTIO_BLK_F_TOPOLOGY	(1 << 10)	/* Topology information is available */
+#define VIRTIO_BLK_F_CONFIG_WCE (1 << 11)	/* Writeback mode available in config */
+#define VIRTIO_BLK_F_MQ		(1 << 12)	/* Multi-Queue */
+#define VIRTIO_BLK_F_DISCARD	(1 << 13)	/* Trim blocks */
+#define VIRTIO_BLK_F_WRITE_ZEROES (1 << 14)	/* Write zeros */
 
 #define VIRTIO_BLK_ID_BYTES	20	/* ID string length */
 
@@ -74,7 +78,15 @@
 
 	/* Writeback mode (if VIRTIO_BLK_F_CONFIG_WCE) */
 	uint8_t writeback;
-
+	uint8_t unused0[1];
+	uint16_t num_queues;
+	uint32_t max_discard_sectors;
+	uint32_t max_discard_seg;
+	uint32_t discard_sector_alignment;
+	uint32_t max_write_zeroes_sectors;
+	uint32_t max_write_zeroes_seg;
+	uint8_t write_zeroes_may_unmap;
+	uint8_t unused1[3];
 } __packed;
 
 /*
@@ -89,23 +101,34 @@
  */
 
 /* These two define direction. */
-#define VIRTIO_BLK_T_IN		0
-#define VIRTIO_BLK_T_OUT	1
+#define VIRTIO_BLK_T_IN			0
+#define VIRTIO_BLK_T_OUT		1
 
 /* This bit says it's a scsi command, not an actual read or write. */
-#define VIRTIO_BLK_T_SCSI_CMD	2
+#define VIRTIO_BLK_T_SCSI_CMD		2
+#define VIRTIO_BLK_T_SCSI_CMD_OUT	3
 
 /* Cache flush command */
-#define VIRTIO_BLK_T_FLUSH	4
+#define VIRTIO_BLK_T_FLUSH		4
+#define VIRTIO_BLK_T_FLUSH_OUT		5
 
 /* Get device ID command */
-#define VIRTIO_BLK_T_GET_ID	8
+#define VIRTIO_BLK_T_GET_ID		8
+
+/* Discard command */
+#define VIRTIO_BLK_T_DISCARD		11
+
+/* Write zeros command */
+#define VIRTIO_BLK_T_WRITE_ZEROES	13
 
 /* Barrier before this op. */
-#define VIRTIO_BLK_T_BARRIER	0x80000000
+#define VIRTIO_BLK_T_BARRIER		0x80000000
 
 /* ID string length */
-#define VIRTIO_BLK_ID_BYTES	20
+#define VIRTIO_BLK_ID_BYTES		20
+
+/* Unmap this range (only valid for write zeroes command) */
+#define VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP	0x00000001
 
 /* This is the first element of the read scatter-gather list. */
 struct virtio_blk_outhdr {
@@ -117,6 +140,15 @@
 	uint64_t sector;
 };
 
+struct virtio_blk_discard_write_zeroes {
+	uint64_t sector;
+	uint32_t num_sectors;
+	struct {
+		uint32_t unmap:1;
+		uint32_t reserved:31;
+	} flags;
+};
+
 struct virtio_scsi_inhdr {
 	uint32_t errors;
 	uint32_t data_len;
Index: sys/dev/virtio/block/virtio_blk.c
===================================================================
--- sys/dev/virtio/block/virtio_blk.c
+++ sys/dev/virtio/block/virtio_blk.c
@@ -81,6 +81,7 @@
 #define VTBLK_FLAG_SUSPEND	0x0008
 #define VTBLK_FLAG_BARRIER	0x0010
 #define VTBLK_FLAG_WC_CONFIG	0x0020
+#define VTBLK_FLAG_DISCARD	0x0040
 
 	struct virtqueue	*vtblk_vq;
 	struct sglist		*vtblk_sglist;
@@ -112,6 +113,7 @@
 	{ VIRTIO_BLK_F_WCE,		"WriteCache"	},
 	{ VIRTIO_BLK_F_TOPOLOGY,	"Topology"	},
 	{ VIRTIO_BLK_F_CONFIG_WCE,	"ConfigWCE"	},
+	{ VIRTIO_BLK_F_DISCARD,		"Discard"	},
 
 	{ 0, NULL }
 };
@@ -210,6 +212,7 @@
      VIRTIO_BLK_F_WCE			| \
      VIRTIO_BLK_F_TOPOLOGY		| \
      VIRTIO_BLK_F_CONFIG_WCE		| \
+     VIRTIO_BLK_F_DISCARD		| \
      VIRTIO_RING_F_INDIRECT_DESC)
 
 #define VTBLK_MTX(_sc)		&(_sc)->vtblk_mtx
@@ -544,7 +547,8 @@
 	 * be a better way to report our readonly'ness to GEOM above.
 	 */
 	if (sc->vtblk_flags & VTBLK_FLAG_READONLY &&
-	    (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) {
+	    (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH ||
+	    bp->bio_cmd == BIO_DELETE)) {
 		vtblk_bio_done(sc, bp, EROFS);
 		return;
 	}
@@ -592,6 +596,8 @@
 		sc->vtblk_flags |= VTBLK_FLAG_BARRIER;
 	if (virtio_with_feature(dev, VIRTIO_BLK_F_CONFIG_WCE))
 		sc->vtblk_flags |= VTBLK_FLAG_WC_CONFIG;
+	if (virtio_with_feature(dev, VIRTIO_BLK_F_DISCARD))
+		sc->vtblk_flags |= VTBLK_FLAG_DISCARD;
 }
 
 static int
@@ -720,6 +726,12 @@
 		    dp->d_stripesize;
 	}
 
+	if (virtio_with_feature(dev, VIRTIO_BLK_F_DISCARD)) {
+		dp->d_flags |= DISKFLAG_CANDELETE;
+		dp->d_delmaxsize = blkcfg->max_discard_sectors *
+		    dp->d_sectorsize;
+	}
+
 	if (vtblk_write_cache_enabled(sc, blkcfg) != 0)
 		sc->vtblk_write_cache = VTBLK_CACHE_WRITEBACK;
 	else
@@ -876,6 +888,9 @@
 		req->vbr_hdr.type = VIRTIO_BLK_T_OUT;
 		req->vbr_hdr.sector = bp->bio_offset / 512;
 		break;
+	case BIO_DELETE:
+		req->vbr_hdr.type = VIRTIO_BLK_T_DISCARD;
+		break;
 	default:
 		panic("%s: bio with unhandled cmd: %d", __func__, bp->bio_cmd);
 	}
@@ -929,6 +944,16 @@
 		/* BIO_READ means the host writes into our buffer. */
 		if (bp->bio_cmd == BIO_READ)
 			writable = sg->sg_nseg - 1;
+	} else if (bp->bio_cmd == BIO_DELETE) {
+		struct virtio_blk_discard_write_zeroes discard;
+
+		discard.sector = bp->bio_offset / 512;
+		discard.num_sectors = bp->bio_bcount / 512;
+		error = sglist_append(sg, &discard, sizeof(discard));
+		if (error || sg->sg_nseg == sg->sg_maxseg) {
+			panic("%s: bio %p data buffer too big %d",
+			    __func__, bp, error);
+		}
 	}
 
 	writable++;
@@ -1119,6 +1144,11 @@
 	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_BLK_SIZE, blk_size, blkcfg);
 	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_TOPOLOGY, topology, blkcfg);
 	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_CONFIG_WCE, writeback, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_DISCARD, max_discard_sectors,
+	    blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_DISCARD, max_discard_seg, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_DISCARD, discard_sector_alignment,
+	    blkcfg);
 }
 
 #undef VTBLK_GET_CONFIG