virtio-blk not work in freebsd guest with qemu>=7.0.0

[faicker]

Sighting report

virtio-blk device with vhost-user/spdk as BE can't be used in freebsd 14.0 guest.

Expected Behavior

can be used.

Current Behavior

In qemu 8.2.0, when a virtio-blk device with vhost-user/spdk as bE is attached to freebsd 14.0 guest,
the guest show errors,
host requires unsupported maximum segment size feature. attach returned 45

the error is from,
https://github.com/freebsd/freebsd-src/blob/release/14.0.0/sys/dev/virtio/block/virtio_blk.c#L348

qemu add the feature VIRTIO_BLK_F_SIZE_MAX from the commit qemu/qemu@0a963af

from spdk,
https://github.com/spdk/spdk/blob/master/lib/vhost/vhost_blk.c#L1524

the max is,
#define SPDK_BDEV_LARGE_BUF_MAX_SIZE (64 * 1024)

But the freebsd 14.0 maxphys default is 1M.
freebsd/freebsd-src@cd85379

[changpe1]

@faicker I don't think this is a SPDK bug, but I'm OK to workaround it in SPDK, e.g: we may introduce a flag not to enable VIRTIO_BLK_F_SIZE_MAX feature bit for FreeBSD VM.

[faicker]

Maybe qemu should export a cmdline flag to disable the VIRTIO_BLK_F_SIZE_MAX.
I'll post to the qemu issues.

[xjjx]

@faicker are there any news? Did you have a chance to post issue to QEMU?

[faicker]

Sorry for late post.
The issue on qemu is here,
https://gitlab.com/qemu-project/qemu/-/issues/2289