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Tsirkin" To: Jason Wang Cc: linux-kernel , stable@vger.kernel.org, Xie Yongji , Paolo Bonzini , Stefan Hajnoczi , Jens Axboe , virtualization , linux-block@vger.kernel.org Subject: Re: [PATCH] Revert "virtio-blk: Add validation for block size in config space" Message-ID: <20211014015029-mutt-send-email-mst@kernel.org> References: <20211013124553.23803-1-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Oct 14, 2021 at 10:45:25AM +0800, Jason Wang wrote: > On Wed, Oct 13, 2021 at 8:46 PM Michael S. Tsirkin 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 think what we should do is fix upstream QEMU first. With that, plus Halil's work-around writing out the version 1 feature, we should be good reading config in validate. > > 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()). That's not a bad idea anyway - any validation that does not need to clear features can be done in probe in any case. > > 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 > > Signed-off-by: Michael S. Tsirkin > > Acked-by: jason Wang > > > --- > > 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 > >