Re: [PATCH v2 09/13] qemu: Fill in model of 'usb' disks to preserve ABI compatibility

On Mon, Jun 23, 2025 at 21:59:14 +0200, Peter Krempa wrote: > From: Peter Krempa <pkrempa(a)redhat.com&gt; > > While 'usb-bot' and 'usb-storage' are ABI and migration compatible for > disks it's not the case for cdroms. When migrating from a new config > using 'usb-bot' to an older daemon which would use 'usb-storage' the > guest os will get I/O errors. > > Thus we must properly fill in models for 'usb' disks so that cdroms can > be handled properly. > > When parsing XML fill in the models and drop the appropriate models when > formatting migratable XML. > > The logic is explained in comments in the code. > > Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; > --- > src/qemu/qemu_domain.c | 21 ++++++++ > src/qemu/qemu_postparse.c | 49 ++++++++++++++++++- > src/qemu/qemu_postparse.h | 4 +- > tests/qemublocktest.c | 13 +++-- > .../qemuhotplug-base-live+cdrom-usb.xml | 2 +- > .../qemuhotplug-base-live+disk-usb.xml | 2 +- > .../disk-cache.x86_64-latest.xml | 2 +- > .../disk-usb-device-model.x86_64-latest.xml | 4 +- > ...test.QEMU_CAPS_DEVICE_USB_BOT-disabled.xml | 24 ++++----- > ...date.QEMU_CAPS_DEVICE_USB_BOT-disabled.xml | 24 ++++----- > ...sk-usb-device.x86_64-latest.abi-update.xml | 24 ++++----- > .../disk-usb-device.x86_64-latest.xml | 24 ++++----- > 12 files changed, 132 insertions(+), 61 deletions(-)

The logic is OK. I guess my comment in the previous patch was actually about using VIR_DOMAIN_DEF_PARSE_ABI_UPDATE flag. But you're not touching this part here so I guess everything should be fine. Although I'm still surprised we'd allow ABI update when starting a domain, I thought this was only allowed when defining it... > /* default disk encryption engine */ > for (n = disk->src; virStorageSourceIsBacking(n); n = n->backingStore) { > if (n->encryption && n->encryption->engine == VIR_STORAGE_ENCRYPTION_ENGINE_DEFAULT)