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.