* Stefano Garzarella (sgarz...@redhat.com) wrote:
> This patch adds the support of DISCARD and WRITE ZEROES commands,
> that have been introduced in the virtio-blk protocol to have
> better performance when using SSD backend.
>
> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
Hi,
Do you need to make those features machine-type dependent
so that a VM started on a nice new qemu with this feature doesn't
get confused when live migrated back to an older version?
Dave
> ---
> hw/block/virtio-blk.c | 79 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 79 insertions(+)
>
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index f208c6ddb9..8850957751 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -145,6 +145,25 @@ out:
> aio_context_release(blk_get_aio_context(s->conf.conf.blk));
> }
>
> +static void virtio_blk_discard_wzeroes_complete(void *opaque, int ret)
> +{
> + VirtIOBlockReq *req = opaque;
> + VirtIOBlock *s = req->dev;
> +
> + aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
> + if (ret) {
> + if (virtio_blk_handle_rw_error(req, -ret, 0)) {
> + goto out;
> + }
> + }
> +
> + virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
> + virtio_blk_free_request(req);
> +
> +out:
> + aio_context_release(blk_get_aio_context(s->conf.conf.blk));
> +}
> +
> #ifdef __linux__
>
> typedef struct {
> @@ -584,6 +603,56 @@ static int virtio_blk_handle_request(VirtIOBlockReq
> *req, MultiReqBuffer *mrb)
> virtio_blk_free_request(req);
> break;
> }
> + /*
> + * VIRTIO_BLK_T_DISCARD and VIRTIO_BLK_T_WRITE_ZEROES are defined with
> + * VIRTIO_BLK_T_OUT flag set. We masked this flag in the switch
> statement,
> + * so we must mask it for these requests, then we will check the type.
> + */
> + case VIRTIO_BLK_T_DISCARD & ~VIRTIO_BLK_T_OUT:
> + case VIRTIO_BLK_T_WRITE_ZEROES & ~VIRTIO_BLK_T_OUT:
> + {
> + struct virtio_blk_discard_write_zeroes dwz_hdr;
> + uint64_t sector;
> + int bytes;
> +
> + if (unlikely(iov_to_buf(out_iov, out_num, 0, &dwz_hdr,
> + sizeof(dwz_hdr)) != sizeof(dwz_hdr))) {
> + virtio_error(vdev, "virtio-blk discard/wzeroes header too
> short");
> + return -1;
> + }
> +
> + sector = virtio_ldq_p(VIRTIO_DEVICE(req->dev), &dwz_hdr.sector);
> + bytes = virtio_ldl_p(VIRTIO_DEVICE(req->dev),
> + &dwz_hdr.num_sectors) << BDRV_SECTOR_BITS;
> +
> + if (!virtio_blk_sect_range_ok(req->dev, sector, bytes)) {
> + virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
> + virtio_blk_free_request(req);
> + return 0;
> + }
> +
> + if ((type & ~(VIRTIO_BLK_T_BARRIER)) == VIRTIO_BLK_T_DISCARD) {
> + blk_aio_pdiscard(req->dev->blk, sector << BDRV_SECTOR_BITS,
> bytes,
> + virtio_blk_discard_wzeroes_complete, req);
> + } else if ((type & ~(VIRTIO_BLK_T_BARRIER)) ==
> + VIRTIO_BLK_T_WRITE_ZEROES) {
> + int flags = 0;
> +
> + if (virtio_ldl_p(VIRTIO_DEVICE(req->dev), &dwz_hdr.flags) &
> + VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
> + flags |= BDRV_REQ_MAY_UNMAP;
> + }
> +
> + blk_aio_pwrite_zeroes(req->dev->blk, sector << BDRV_SECTOR_BITS,
> + bytes, flags,
> + virtio_blk_discard_wzeroes_complete, req);
> + } else { /* Unsupported if VIRTIO_BLK_T_OUT is not set */
> + virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
> + virtio_blk_free_request(req);
> + }
> +
> + break;
> + }
> default:
> virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
> virtio_blk_free_request(req);
> @@ -763,6 +832,14 @@ static void virtio_blk_update_config(VirtIODevice *vdev,
> uint8_t *config)
> blkcfg.alignment_offset = 0;
> blkcfg.wce = blk_enable_write_cache(s->blk);
> virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
> + virtio_stl_p(vdev, &blkcfg.max_discard_sectors,
> BDRV_REQUEST_MAX_SECTORS);
> + virtio_stl_p(vdev, &blkcfg.max_discard_seg, 1);
> + virtio_stl_p(vdev, &blkcfg.discard_sector_alignment,
> + blk_size >> BDRV_SECTOR_BITS);
> + virtio_stl_p(vdev, &blkcfg.max_write_zeroes_sectors,
> + BDRV_REQUEST_MAX_SECTORS);
> + virtio_stl_p(vdev, &blkcfg.max_write_zeroes_seg, 1);
> + blkcfg.write_zeroes_may_unmap = 1;
> memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
> }
>
> @@ -787,6 +864,8 @@ static uint64_t virtio_blk_get_features(VirtIODevice
> *vdev, uint64_t features,
> virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
> virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
> virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
> + virtio_add_feature(&features, VIRTIO_BLK_F_DISCARD);
> + virtio_add_feature(&features, VIRTIO_BLK_F_WRITE_ZEROES);
> if (virtio_has_feature(features, VIRTIO_F_VERSION_1)) {
> if (s->conf.scsi) {
> error_setg(errp, "Please set scsi=off for virtio-blk devices in
> order to use virtio 1.0");
> --
> 2.20.1
>
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
