Re: [Qemu-devel] [PATCH v2] pc: allow raising low memory via max-ram-below-4g option

[Gerd Hoffmann]

On Mi, 2016-01-20 at 19:25 +0200, Michael S. Tsirkin wrote:
> On Wed, Jan 20, 2016 at 03:15:04PM -0200, Eduardo Habkost wrote:
> > On Wed, Jan 20, 2016 at 01:34:29PM -0200, Eduardo Habkost wrote:
> > [...]
> > > Considering that we never supported
> > >   gigabyte_align && max_ram_below_4g > 3G ||
> > >   max_ram_below_4g > 3.5G
> > > before, we could simply remove the MachineClass::gigabyte_align
> > > field from pc_piix, and just do the following:
> > > 
> > > * pc > 1.7: max_ram_below_4g = 3G
> > >   (equivalent to gigabyte_align=true)
> > > * pc <= 1.7: max_ram_below_4g = 3.5G
> > >   (equivalent to gigabyte_align=false)
> > 
> > Ignore the suggestion above. I forgot that gigabyte_align applies
> > only if ram_size > 3.5GB (so setting max_ram_below_4g = 3G on
> > pc > 1.7 wouldn't work). So, unless somebody has a suggestion
> > that makes this logic simpler:
> 
> I wonder whether we should just bite the bullet and ask management to
> maintain the physical memory map for us, instead of trying to give us
> hints.

I doubt this simplified things, given the backward compatibility
constrains we have.

cheers,
  Gerd