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

["Michael S. Tsirkin" <mst@redhat.com>]

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.

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