Re: [Qemu-devel] [patch 2/2] i386: pc: align gpa<->hpa on 1GB boundary

[Paolo Bonzini]

Il 30/10/2013 12:07, Gerd Hoffmann ha scritto:
> On Fr, 2013-10-25 at 23:53 +0100, Paolo Bonzini wrote:
>> Il 25/10/2013 20:50, Marcelo Tosatti ha scritto:
>>> On Fri, Oct 25, 2013 at 09:52:34AM +0100, Paolo Bonzini wrote:
>>>> Because offsets are zero, and lengths match the RAM block lengths, you
>>>> do not need any complication with aliasing.  This still has to be done
>>>> only for new machine types.
>>>
>>> Not possible because you just wasted holesize bytes (if number of
>>> additional bytes due to huge page alignment is smaller than holesize, a
>>> new hugepage is required, which is not acceptable).
>>
>> Ok.  Thanks for explaining---the patch seems good with the proper
>> compatibility option in the machine type.  Please run the
>> guest_memory_dump_analysis test in autotest too.
> 
> As the whole thing must depend on machine type anyway for live migration
> compatibility we can also simply change the memory split, i.e. map 2GB
> (-M q35) or 3GB (-M pc) below 4G instead of the odd sizes (2.75 / 3.5)
> we have now.

For q35 it could be a possibility.  For pc, I'm worried about old
Windows systems that ignore all memory outside the first 4GB.  They
would lose 512 MB of memory.

Paolo