Re: [PATCH] virtio-blk: drop deprecated scsi=on|off property
Eduardo Habkost <ehabkost(a)redhat.com> writes:
On Thu, Apr 29, 2021 at 04:52:21PM +0100, Stefan Hajnoczi wrote:
> The scsi=on|off property was deprecated in QEMU 5.0 and can be removed
> completely at this point.
>
> Drop the scsi=on|off option. It was only available on Legacy virtio-blk
> devices. Linux v5.6 already dropped support for it.
>
> Remove the hw_compat_2_4[] property assignment since scsi=on|off no
> longer exists. Old guests with Legacy virtio-blk devices no longer see
> the SCSI host features bit.
>
This means pc-2.4 will now break guest ABI if using virtio-blk
devices, correct?
This looks like a sign we should have deprecated pc-2.4 a long
time ago.
The last batch of PC machine type retiring was pc-1.0 to pc-1.3:
deprecated in 5.0 (commit 30d2a17b4, Dec 2019), dropped in 6.0 (commit
f862ddbb1, just weeks ago). pc-1.3 was a bit over seven years old when
we released 5.0. pc-2.4 will be six years old by the time we release
6.1. Fair game?
> Live migrating old guests from an old QEMU with the SCSI feature
bit
> enabled will fail with "Features 0x... unsupported. Allowed features:
> 0x...". We've followed the QEMU deprecation policy so users have been
> warned...
>
Were they really warned, though? People running
"-machine pc-i440fx-2.4" might be completely unaware that it was
silently enabling a deprecated feature.
We've gotten better at documenting deprecations, but we're still bad at
warning on use of deprecated features.
[...]