vdpa_sim_blk: add support for discard and write-zeroes

Expose VIRTIO_BLK_F_DISCARD and VIRTIO_BLK_F_WRITE_ZEROES features
to the drivers and handle VIRTIO_BLK_T_DISCARD and
VIRTIO_BLK_T_WRITE_ZEROES requests checking ranges and flags.

The simulator behaves like a ramdisk, so for VIRTIO_BLK_F_DISCARD
does nothing, while for VIRTIO_BLK_T_WRITE_ZEROES sets to 0 the
specified region.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20220811083632.77525-5-sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim_blk.c

@@ -30,11 +30,14 @@
 				 (1ULL << VIRTIO_BLK_F_SEG_MAX)  | \
 				 (1ULL << VIRTIO_BLK_F_BLK_SIZE) | \
 				 (1ULL << VIRTIO_BLK_F_TOPOLOGY) | \
-				 (1ULL << VIRTIO_BLK_F_MQ))
+				 (1ULL << VIRTIO_BLK_F_MQ)       | \
+				 (1ULL << VIRTIO_BLK_F_DISCARD)  | \
+				 (1ULL << VIRTIO_BLK_F_WRITE_ZEROES))
 
 #define VDPASIM_BLK_CAPACITY	0x40000
 #define VDPASIM_BLK_SIZE_MAX	0x1000
 #define VDPASIM_BLK_SEG_MAX	32
+#define VDPASIM_BLK_DWZ_MAX_SECTORS UINT_MAX
 
 /* 1 virtqueue, 1 address space, 1 virtqueue group */
 #define VDPASIM_BLK_VQ_NUM	1
@@ -193,6 +196,64 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
 		/* nothing to do */
 		break;
 
+	case VIRTIO_BLK_T_DISCARD:
+	case VIRTIO_BLK_T_WRITE_ZEROES: {
+		struct virtio_blk_discard_write_zeroes range;
+		u32 num_sectors, flags;
+
+		if (to_pull != sizeof(range)) {
+			dev_dbg(&vdpasim->vdpa.dev,
+				"discard/write_zeroes header len: 0x%zx [expected: 0x%zx]\n",
+				to_pull, sizeof(range));
+			status = VIRTIO_BLK_S_IOERR;
+			break;
+		}
+
+		bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->out_iov, &range,
+					      to_pull);
+		if (bytes < 0) {
+			dev_dbg(&vdpasim->vdpa.dev,
+				"vringh_iov_pull_iotlb() error: %zd offset: 0x%llx len: 0x%zx\n",
+				bytes, offset, to_pull);
+			status = VIRTIO_BLK_S_IOERR;
+			break;
+		}
+
+		sector = le64_to_cpu(range.sector);
+		offset = sector << SECTOR_SHIFT;
+		num_sectors = le32_to_cpu(range.num_sectors);
+		flags = le32_to_cpu(range.flags);
+
+		if (type == VIRTIO_BLK_T_DISCARD && flags != 0) {
+			dev_dbg(&vdpasim->vdpa.dev,
+				"discard unexpected flags set - flags: 0x%x\n",
+				flags);
+			status = VIRTIO_BLK_S_UNSUPP;
+			break;
+		}
+
+		if (type == VIRTIO_BLK_T_WRITE_ZEROES &&
+		    flags & ~VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
+			dev_dbg(&vdpasim->vdpa.dev,
+				"write_zeroes unexpected flags set - flags: 0x%x\n",
+				flags);
+			status = VIRTIO_BLK_S_UNSUPP;
+			break;
+		}
+
+		if (!vdpasim_blk_check_range(vdpasim, sector, num_sectors,
+					     VDPASIM_BLK_DWZ_MAX_SECTORS)) {
+			status = VIRTIO_BLK_S_IOERR;
+			break;
+		}
+
+		if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
+			memset(vdpasim->buffer + offset, 0,
+			       num_sectors << SECTOR_SHIFT);
+		}
+
+		break;
+	}
 	default:
 		dev_dbg(&vdpasim->vdpa.dev,
 			"Unsupported request type %d\n", type);
@@ -281,6 +342,17 @@ static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
 	blk_config->min_io_size = cpu_to_vdpasim16(vdpasim, 1);
 	blk_config->opt_io_size = cpu_to_vdpasim32(vdpasim, 1);
 	blk_config->blk_size = cpu_to_vdpasim32(vdpasim, SECTOR_SIZE);
+	/* VIRTIO_BLK_F_DISCARD */
+	blk_config->discard_sector_alignment =
+		cpu_to_vdpasim32(vdpasim, SECTOR_SIZE);
+	blk_config->max_discard_sectors =
+		cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_DWZ_MAX_SECTORS);
+	blk_config->max_discard_seg = cpu_to_vdpasim32(vdpasim, 1);
+	/* VIRTIO_BLK_F_WRITE_ZEROES */
+	blk_config->max_write_zeroes_sectors =
+		cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_DWZ_MAX_SECTORS);
+	blk_config->max_write_zeroes_seg = cpu_to_vdpasim32(vdpasim, 1);
+
 }
 
 static void vdpasim_blk_mgmtdev_release(struct device *dev)