From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:42533) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtYFh-0008Rs-OO for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:37:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtYFd-0000Ot-NM for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:37:33 -0500 Received: from 2.mo5.mail-out.ovh.net ([178.33.109.111]:51038) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gtYFb-0008Qn-D6 for qemu-devel@nongnu.org; Tue, 12 Feb 2019 08:37:27 -0500 Received: from player694.ha.ovh.net (unknown [10.109.160.253]) by mo5.mail-out.ovh.net (Postfix) with ESMTP id A483A213F7C for ; Tue, 12 Feb 2019 14:37:12 +0100 (CET) Date: Tue, 12 Feb 2019 14:37:00 +0100 From: Greg Kurz Message-ID: <20190212143700.444c2b86@bahia.lan> In-Reply-To: <1549951304-26100-1-git-send-email-changpeng.liu@intel.com> References: <1549951304-26100-1-git-send-email-changpeng.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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, ldoktor@redhat.com, mst@redhat.com, dgilbert@redhat.com, stefanha@redhat.com, sgarzare@redhat.com On Tue, 12 Feb 2019 14:01:44 +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 A hint about the breakage is often a good practice, as it helps people to find the fix if they hit the issue. > will break the migration. While here, set the correct config size "While here" usually means that the corresponding change isn't strictly needed. I don't believe this is the case here since fixing the config size is precisely the goal of this patch. > when initializing the host driver, for now, discard/write zeroes > are not supported by virtio-blk host driver, so set the config As mentioned by Michael, there's no such thing as a "host driver". Just say virtio-blk. > size as before, users can change config size when adding the new > feature bits support. > What about ? 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 > --- LGTM Reviewed-by: Greg Kurz Tested-by: Greg Kurz > 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)) > + > 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); > } > > 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); > > 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;