On Wed, Oct 13, 2021 at 8:46 PM Michael S. Tsirkin mst@redhat.com wrote:
It turns out that access to config space before completing the feature negotiation is broken for big endian guests at least with QEMU hosts up to 6.1 inclusive. This affects any device that accesses config space in the validate callback: at the moment that is virtio-net with VIRTIO_NET_F_MTU but since 82e89ea077b9 ("virtio-blk: Add validation for block size in config space") that also started affecting virtio-blk with VIRTIO_BLK_F_BLK_SIZE.
Ok, so it looks like I need to do something similar in my series to validate max_nr_ports in probe() instead of validate()? (multi port is not enabled by default).
I wonder if we need to document this and rename the validate to validate_features() (since we can do very little thing if we can't read config in .validate()).
Further, unlike VIRTIO_NET_F_MTU which is off by default on QEMU, VIRTIO_BLK_F_BLK_SIZE is on by default, which resulted in lots of people not being able to boot VMs on BE.
The spec is very clear that what we are doing is legal so QEMU needs to be fixed, but given it's been broken for so many years and no one noticed, we need to give QEMU a bit more time before applying this.
Further, this patch is incomplete (does not check blk size is a power of two) and it duplicates the logic from nbd.
Revert for now, and we'll reapply a cleaner logic in the next release.
Cc: stable@vger.kernel.org Fixes: 82e89ea077b9 ("virtio-blk: Add validation for block size in config space") Cc: Xie Yongji xieyongji@bytedance.com Signed-off-by: Michael S. Tsirkin mst@redhat.com
Acked-by: jason Wang jasowang@redhat.com
drivers/block/virtio_blk.c | 37 ++++++------------------------------- 1 file changed, 6 insertions(+), 31 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 9b3bd083b411..303caf2d17d0 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -689,28 +689,6 @@ static const struct blk_mq_ops virtio_mq_ops = { static unsigned int virtblk_queue_depth; module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
-static int virtblk_validate(struct virtio_device *vdev) -{
u32 blk_size;if (!vdev->config->get) {dev_err(&vdev->dev, "%s failure: config access disabled\n",__func__);return -EINVAL;}if (!virtio_has_feature(vdev, VIRTIO_BLK_F_BLK_SIZE))return 0;blk_size = virtio_cread32(vdev,offsetof(struct virtio_blk_config, blk_size));if (blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE)__virtio_clear_bit(vdev, VIRTIO_BLK_F_BLK_SIZE);return 0;-}
static int virtblk_probe(struct virtio_device *vdev) { struct virtio_blk *vblk; @@ -722,6 +700,12 @@ static int virtblk_probe(struct virtio_device *vdev) u8 physical_block_exp, alignment_offset; unsigned int queue_depth;
if (!vdev->config->get) {dev_err(&vdev->dev, "%s failure: config access disabled\n",__func__);return -EINVAL;}err = ida_simple_get(&vd_index_ida, 0, minor_to_index(1 << MINORBITS), GFP_KERNEL); if (err < 0)@@ -836,14 +820,6 @@ static int virtblk_probe(struct virtio_device *vdev) else blk_size = queue_logical_block_size(q);
if (blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE) {dev_err(&vdev->dev,"block size is changed unexpectedly, now is %u\n",blk_size);err = -EINVAL;goto out_cleanup_disk;}/* Use topology information if available */ err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY, struct virtio_blk_config, physical_block_exp,@@ -1009,7 +985,6 @@ static struct virtio_driver virtio_blk = { .driver.name = KBUILD_MODNAME, .driver.owner = THIS_MODULE, .id_table = id_table,
.validate = virtblk_validate, .probe = virtblk_probe, .remove = virtblk_remove, .config_changed = virtblk_config_changed,-- MST