From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:44695) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtZqk-0001nX-PW for qemu-devel@nongnu.org; Tue, 12 Feb 2019 10:19:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtZqj-0008W5-Hg for qemu-devel@nongnu.org; Tue, 12 Feb 2019 10:19:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40474) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gtZqj-0008Nc-91 for qemu-devel@nongnu.org; Tue, 12 Feb 2019 10:19:53 -0500 Date: Tue, 12 Feb 2019 10:11:28 -0500 From: "Michael S. Tsirkin" Message-ID: <20190212101028-mutt-send-email-mst@kernel.org> References: <1549984789-26997-1-git-send-email-changpeng.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1549984789-26997-1-git-send-email-changpeng.liu@intel.com> Subject: Re: [Qemu-devel] [PATCH v3] 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 11:19:49PM +0800, Changpeng Liu wrote: > Commit caa1ee43 "vhost-user-blk: add discard/write zeroes features > support" added fields to struct virtio_blk_config. This changes > the size of the config space and breaks migration from QEMU 3.1 > and older: > > qemu-system-ppc64: get_pci_config_device: Bad config data: i=0x10 read: 41 device: 1 cmask: ff wmask: 80 w1cmask:0 > qemu-system-ppc64: Failed to load PCIDevice:config > qemu-system-ppc64: Failed to load virtio-blk:virtio > qemu-system-ppc64: error while loading state for instance 0x0 of device 'pci@800000020000000:01.0/virtio-blk' > qemu-system-ppc64: load of migration failed: Invalid argument > > Since virtio-blk doesn't support the "discard" and "write zeroes" > features, it shouldn't even expose the associated fields in the > config space actually. Just include all fields up to num_queues to > match QEMU 3.1 and older. > > Signed-off-by: Changpeng Liu OK almost. > --- > hw/block/virtio-blk.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 9a87b3b..0ff5315 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -28,6 +28,10 @@ > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio-access.h" > > +/* We don't support discard yet, hide associated config fields. */ > +#define VIRTIO_BLK_CFG_SIZE offsetof(struct virtio_blk_config, \ > + max_discard_sectors) > + > static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq, > VirtIOBlockReq *req) > { > @@ -761,7 +765,9 @@ 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); > + QEMU_BUILD_BUG_ON(VIRTIO_BLK_CFG_SIZE > sizeof(struct virtio_blk_config)); > + Oh probably sizeof blkcfg here, right? Also we don't need the empty line here. > } > > static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) > @@ -769,7 +775,8 @@ 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); > + 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 +959,7 @@ 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