On Wed, 13 Feb 2019 09:48:57 +0800
Changpeng Liu <changpeng....@intel.com> 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 <changpeng....@intel.com>
> ---
Again ;-)
Reviewed-by: Greg Kurz <gr...@kaod.org>
Tested-by: Greg Kurz <gr...@kaod.org>
> hw/block/virtio-blk.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 9a87b3b..6fce9c7 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 +765,8 @@ 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(blkcfg));
> }
>
> static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
> @@ -769,7 +774,8 @@ 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 +958,7 @@ 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;
