On Thu, May 15, 2014 at 11:34:25AM +0530, Amit Shah wrote: > 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
This calls for a way for devices to inherit properties from the bus, which doesn't exist ATM. Fine but let's not hold up this patchset because of this. -- MST
