On (Wed) 14 May 2014 [17:41:38], Greg Kurz wrote: > There is a need to add some more fields to VirtIODevice that should be > migrated (broken status, endianness). The problem is that we do not > want to break compatibility while adding a new feature... This issue has > been addressed in the generic VMState code with the use of optional > subsections. As a *temporary* alternative to port the whole virtio > migration code to VMState, this patch mimics a similar subsectionning > ability for virtio. > > Since each virtio device is streamed in its own section, the idea is to > stream subsections between the end of the device section and the start > of the next sections. This allows an older QEMU to complain and exit > when fed with subsections: > > Unknown savevm section type 5 > Error -22 while loading VM state
Please make this configurable -- either via configure or device properties. That avoids having to break existing configurations that work without this patch. > All users of virtio_load()/virtio_save() need to be patched because the > subsections are streamed AFTER the device itself. Since all have the same fixup, I'm wondering if a new section can be added to the virtio-bus itself, which gets propagated to all devices upon load in the dest. Amit