Re: [Qemu-devel] [PATCH for-1.6 0/2] future proof rom loading for cross versiom migration

[Anthony Liguori <aliguori@us.ibm.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> ROM files that are put in FW CFG are copied to guest ram, by BIOS, but
> they are not backed by RAM so they don't get migrated.
>
> Each time we'll change at least two bytes in such a ROM this will break
> cross-version migration: since we can migrate after BIOS has read the first
> byte but before it has read the second one, getting an inconsistent state.
>
> This patchset makes QEMU future-proof against such changes.
>
> Naturally, this only helps for -M 1.6 and up, older machine types
> will still have the cross-version migration bug.
>
> I think this should be applied for 1.6, this way we won't
> have this problem from 1.7 and on.

This is not for 1.6.  It's far too late to make a change like this.

Regards,

Anthony Liguori

>
> Michael S. Tsirkin (2):
>   memory: export target page size
>   loader: put FW CFG ROM files into RAM
>
>  exec.c                |  2 ++
>  hw/core/loader.c      | 54 ++++++++++++++++++++++++++++++++++++++++++++++++---
>  hw/i386/pc_piix.c     |  2 ++
>  hw/i386/pc_q35.c      |  2 ++
>  include/exec/memory.h |  2 ++
>  include/hw/loader.h   |  1 +
>  6 files changed, 60 insertions(+), 3 deletions(-)
>
> -- 
> MST