From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:45396) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtYQp-0002TB-1W for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:49:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtYQn-0007Xj-Ad for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:49:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47826) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gtYQn-0007Ub-1Z for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:49:01 -0500 Date: Tue, 12 Feb 2019 08:48:54 -0500 From: "Michael S. Tsirkin" Message-ID: <20190212084531-mutt-send-email-mst@kernel.org> References: <1549951304-26100-1-git-send-email-changpeng.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1549951304-26100-1-git-send-email-changpeng.liu@intel.com> Subject: Re: [Qemu-devel] [PATCH v2] 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 02:01:44PM +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 Pls rewrite commit log as suggested in this thread and repost. > --- > hw/block/virtio-blk.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 9a87b3b..846b7b9 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -28,6 +28,9 @@ > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio-access.h" > > +#define VIRTIO_BLK_CFG_SIZE (offsetof(struct virtio_blk_config, num_queues) + \ > + sizeof_field(struct virtio_blk_config, num_queues)) > + I would just do offsetof(max_discard_sectors) with a comment "we don't support discard yet, hide associated config fields". > static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq, > VirtIOBlockReq *req) > { > @@ -761,7 +764,7 @@ 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, VIRTIO_BLK_CFG_SIZE); Let's add QEMU_BUILD_BUG_ON(VIRTIO_BLK_CFG_SIZE <= sizeof(struct virtio_blk_config)) just for documentation purposes. > } > > static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) > @@ -769,7 +772,7 @@ 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, VIRTIO_BLK_CFG_SIZE); Here too, QEMU_BUILD_BUG_ON(VIRTIO_BLK_CFG_SIZE <= sizeof(blkcfg)) > > aio_context_acquire(blk_get_aio_context(s->blk)); > blk_set_enable_write_cache(s->blk, blkcfg.wce != 0); > @@ -952,8 +955,7 @@ 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_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, VIRTIO_BLK_CFG_SIZE); > > s->blk = conf->conf.blk; > s->rq = NULL; > -- > 1.9.3