Re: [Qemu-devel] [PATCH 0/2] pflash (UEFI varstore) migration shortcut for libvirt

[Paolo Bonzini <pbonzini@redhat.com>]

Il 23/08/2014 12:19, Laszlo Ersek ha scritto:
> Libvirt is growing support for x86_64 OVMF guests:
> 
> http://www.redhat.com/archives/libvir-list/2014-August/msg01045.html
> 
> An important feature of such guests is the persistent store for
> non-volatile UEFI variables. This is implemented with if=pflash drives.
> The referenced libvirt patchset sets up the varstore files for
> single-host use.
> 
> Wrt. migration, two choices have been considered:
> (a) full-blown live storage migration for the drives backing pflash
>     devices,
> (b) vs. a shortcut that exploits the special nature of pflash drives
>     (namely, their minuscule size, and a RAMBlock that keeps the full
>     contents of each pflash drive visible to the guest, and is
>     up-to-date, at all times.)
> 
> Patch 1/2 is a trivial cleanup (some DPRINTF() calls in pflash_cfi01
> have bit-rotted). Patch 2/2 seeks to implement choice (b), which is what
> the libvirt patchset relies on for migration.
> 
> Thanks,
> Laszlo
> 
> Laszlo Ersek (2):
>   pflash_cfi01: fixup stale DPRINTF() calls
>   pflash_cfi01: write flash contents to bdrv on incoming migration
> 
>  hw/block/pflash_cfi01.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Alexey/David, I think hw/nvram/spapr_nvram.c should do the same.  It
doesn't have a vmstate, but you can probably use
qemu_add_vm_change_state_handler to the same effect.

Paolo