Re: [PATCH] virtio-blk: use little-endian types for the zoned fields

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Jun 17, 2026 at 11:17:27AM -0400, Michael Bommarito wrote:
> The zoned block-device fields in the virtio-blk header are typed
> __virtio{32,64}, so their endianness follows VIRTIO_F_VERSION_1. The
> zoned feature is only defined for VIRTIO 1.x devices, and the virtio
> specification defines all of its fields as little-endian. Commit
> b16a1756c716 ("virtio_blk: mark all zone fields LE") tagged them
> __le* for exactly this reason, but commit f1ba4e674feb ("virtio-blk:
> fix to match virtio spec") re-applied the reviewed version of the
> original zoned series -- which predated b16a1756 -- and silently
> restored the __virtio* typing together with the matching
> virtio*_to_cpu() / virtio_cread() accessors in the driver.
> 
> Restore the little-endian typing for the zoned configuration-space
> characteristics, the zone descriptor, the zone report header and the
> ZONE_APPEND in-header sector, and read them with le*_to_cpu() and
> virtio_cread_le() to match.
> 
> There is no functional change on any spec-compliant device: zoned
> requires VIRTIO_F_VERSION_1, and for a VERSION_1 device
> virtio*_to_cpu() is identical to le*_to_cpu(). The change makes the
> uapi types describe the actual wire format and removes a latent
> endianness mismatch for a (non-conformant) legacy device on a
> big-endian guest.
> 
> Fixes: f1ba4e674feb ("virtio-blk: fix to match virtio spec")
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
> ---
> Testing:
>  - Builds with no new warnings; sparse endian-clean (C=2,
>    __CHECK_ENDIAN__, CONFIG_BLK_DEV_ZONED=y) both before and after.
>  - Booted under QEMU with a host-managed zoned device exposed through
>    virtio-blk. Zone revalidation, blkzone report and a sequential
>    write / write-pointer check return correct values; blktests zbd
>    device tests 001-006 (sysfs+ioctl, report zone, reset, write split,
>    write ordering, revalidate) pass, with results identical before and
>    after this change -- expected, since on a VIRTIO_F_VERSION_1 device
>    virtio*_to_cpu() == le*_to_cpu().
> 
>  drivers/block/virtio_blk.c      | 38 +++++++++++++++------------------
>  include/uapi/linux/virtio_blk.h | 18 ++++++++--------
>  2 files changed, 26 insertions(+), 30 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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