From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:47647) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmjEL-00034k-UK for qemu-devel@nongnu.org; Thu, 24 Jan 2019 12:55:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gmjEK-0000w6-Oy for qemu-devel@nongnu.org; Thu, 24 Jan 2019 12:55:57 -0500 Date: Thu, 24 Jan 2019 17:55:33 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20190124175533.GC2404@work-vm> References: <20190124172323.230296-1-sgarzare@redhat.com> <20190124172323.230296-2-sgarzare@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190124172323.230296-2-sgarzare@redhat.com> Subject: Re: [Qemu-devel] [PATCH RFC 1/2] virtio-blk: add DISCARD and WRITE ZEROES features List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefano Garzarella Cc: qemu-devel@nongnu.org, Laurent Vivier , Kevin Wolf , Thomas Huth , qemu-block@nongnu.org, "Michael S. Tsirkin" , Max Reitz , Stefan Hajnoczi , Paolo Bonzini * Stefano Garzarella (sgarzare@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 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 / dgilbert@redhat.com / Manchester, UK