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.
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. Can we have this documented in a more explicit way? Maybe just a comment at hw_compat_2_4 would be enough, to warn people doing backports and rebases downstream. Can we make QEMU refuse to start if using pc-2.4 + virtio-blk together, just to be sure? An alternative would be keeping the property (and the hw_compat_2_4 entry) just to keep pc-2.4 working (until pc-2.4 is deprecated and removed), but refusing to realize the device if the feature is enabled.
I have tested that libvirt still works when the property is absent. It no longer adds scsi=on|off to the command-line.
Cc: Markus Armbruster <armbru@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Peter Krempa <pkrempa@redhat.com> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- [...] diff --git a/hw/core/machine.c b/hw/core/machine.c index 40def78183..286f18ec6d 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -194,8 +194,6 @@ GlobalProperty hw_compat_2_5[] = { const size_t hw_compat_2_5_len = G_N_ELEMENTS(hw_compat_2_5);
GlobalProperty hw_compat_2_4[] = { - /* Optional because the 'scsi' property is Linux-only */ - { "virtio-blk-device", "scsi", "true", .optional = true }, { "e1000", "extra_mac_registers", "off" }, { "virtio-pci", "x-disable-pcie", "on" }, { "virtio-pci", "migrate-extra", "off" },
-- Eduardo