Re: [Qemu-devel] [PATCH RFC] ps2: set the keybord output buffer size as the same as kernel

[Gerd Hoffmann]

On Mi, 2014-04-23 at 09:32 +0000, Gonglei (Arei) wrote:
> > 
> > Hi, Gerd and Juan.
> > 
> > Thanks for your guides about the confuse live migration about changing the
> > keyboard buffer size.
> > According your suggestion, I got two solutions to address the issue:
> > 
> > - Keep the data array 256 bytes long, change the rptr/wptr/count/data array 
> > at
> > post_load(), both
> >  Ps/2 keyboard and mouse. This solution can be compatible with older qemu
> > versions, which can
> >  do live migration each other.
> > 
> > -Change the data array to 16 bytes, still save as PS2_QUEUE_SIZE. Reset the
> > rptr/wptr/count at
> > post_load(), both ps/2 keyboard and mouse. Add VMSTATE_UNUSED(256-16) in
> > struct vmstate_ps2_common.
> > This solution just save the 16 bytes buffer and drop the rest, So we can't
> > migrate vm to older qemu versions.
> > But migration from old qemu to new qemu is ok.
> > 
> Sorry, the second solution also support cross-version live migration each 
> other.

But you loose anything in the buffer when migrating from old -> new.

cheers,
  Gerd