Re: [PATCH 2/3] qemu: Replace usb-storage with usb-bot

On Mon, Mar 10, 2025 at 10:10:53AM +0100, Peter Krempa wrote: > On Mon, Mar 10, 2025 at 09:05:28 +0000, Daniel P. Berrangé wrote: > > On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: > > > usb-storage is a compound device that automatically creates a USB mass > > > storage device and a SCSI device as its backend. Unfortunately it lacks > > > some configuration options that are usually present with a SCSI device, > > > and cannot represent CD-ROM in particular. > > > > > > Replace usb-storage with usb-bot, which can be combined with a manually > > > created SCSI device. libvirt will configure the SCSI device in a way > > > identical with how QEMU does for usb-storage except that now it respects > > > a configuration option to represent CD-ROM. > > > > Is this change compatible for QEMU's VMState aka migration ABI compatible ? > > Based on my tests so far it seems compatible in terms of VMstate and > also guest ABI at least to the first glance (lsusb, lsscsi -v etc) seems > identical at least for the default 'read-write'/non-cdrom disk. > > I didn't yet test migrating with a cdrom to an older daemon though, > which based on the above paragraph should have guest-visible difference. Any such configuratin of the latter is arguably a bug though ? It was never presenting a cdrom, and that we allowed it was just a sign of missing XML validation surely ?