From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:39013) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtPjg-0005N3-UB for qemu-devel@nongnu.org; Mon, 11 Feb 2019 23:31:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtPjf-0004TV-K1 for qemu-devel@nongnu.org; Mon, 11 Feb 2019 23:31:56 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40480) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gtPje-0004Fg-Tn for qemu-devel@nongnu.org; Mon, 11 Feb 2019 23:31:55 -0500 Date: Mon, 11 Feb 2019 23:31:28 -0500 From: "Michael S. Tsirkin" Message-ID: <20190211232046-mutt-send-email-mst@kernel.org> References: <1549945516-25643-1-git-send-email-changpeng.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1549945516-25643-1-git-send-email-changpeng.liu@intel.com> Subject: Re: [Qemu-devel] [PATCH] virtio-blk: set correct config size for the host driver List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Changpeng Liu Cc: qemu-devel@nongnu.org, stefanha@redhat.com, sgarzare@redhat.com, dgilbert@redhat.com, ldoktor@redhat.com On Tue, Feb 12, 2019 at 12:25:16PM +0800, Changpeng Liu wrote: > Commit caa1ee43 "vhost-user-blk: add discard/write zeroes features support" > introduced extra fields to existing struct virtio_blk_config, when > migration was executed from older QEMU version to current head, it > will break the migration. While here, set the correct config size > when initializing the host driver, for now, discard/write zeroes > are not supported by virtio-blk host driver, so set the config > size as before, users can change config size when adding the new > feature bits support. > > Signed-off-by: Changpeng Liu > --- > hw/block/virtio-blk.c | 15 +++++++++++---- > include/hw/virtio/virtio-blk.h | 1 + > 2 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 9a87b3b..fac5d33 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -761,7 +761,7 @@ 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); > - memcpy(config, &blkcfg, sizeof(struct virtio_blk_config)); > + memcpy(config, &blkcfg, s->config_size); > } > > static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) > @@ -769,7 +769,7 @@ static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) > VirtIOBlock *s = VIRTIO_BLK(vdev); > struct virtio_blk_config blkcfg; > > - memcpy(&blkcfg, config, sizeof(blkcfg)); > + memcpy(&blkcfg, config, s->config_size); > > aio_context_acquire(blk_get_aio_context(s->blk)); > blk_set_enable_write_cache(s->blk, blkcfg.wce != 0); > @@ -847,6 +847,13 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status) > } > } > > +static void virtio_blk_set_config_size(VirtIOBlock *s) > +{ > + /* VIRTIO_BLK_F_MQ is supported by host driver */ It can be disabled though. It just so happens that only the addition of max_discard_seg crosses the next power of 2 boundary. > + s->config_size = offsetof(struct virtio_blk_config, num_queues) + > + sizeof_field(struct virtio_blk_config, num_queues); > +} > + > static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f) > { > VirtIOBlock *s = VIRTIO_BLK(vdev); > @@ -952,8 +959,8 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp) > return; > } > > - virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, > - sizeof(struct virtio_blk_config)); > + virtio_blk_set_config_size(s); > + virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, s->config_size); > > s->blk = conf->conf.blk; > s->rq = NULL; > diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h > index 5117431..9181a93 100644 > --- a/include/hw/virtio/virtio-blk.h > +++ b/include/hw/virtio/virtio-blk.h > @@ -51,6 +51,7 @@ typedef struct VirtIOBlock { > void *rq; > QEMUBH *bh; > VirtIOBlkConf conf; > + size_t config_size; > unsigned short sector_mask; > bool original_wce; > VMChangeStateEntry *change; Well assuming you are looking for a minimal change, go further and drop config_size completely, replace with a macro. > -- > 1.9.3