Eduardo Habkost <ehabkost@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. [...]