Re: [Qemu-devel] [RFC v0 1/2] spapr: Accommadate alignment gaps in hotplug memory region

[David Gibson]

On Mon, Oct 05, 2015 at 11:05:07AM +0200, Igor Mammedov wrote:
> On Mon,  5 Oct 2015 14:05:23 +0530
> Bharata B Rao <address@hidden> wrote:
> 
> > Size hotplug memory region assuming a 256MB max alignment every slot.
> > 
> > Signed-off-by: Bharata B Rao <address@hidden>
> > ---
> >  hw/ppc/spapr.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index fc5e7d6..2ec509b 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1792,6 +1792,9 @@ static void ppc_spapr_init(MachineState *machine)
> >  
> >          spapr->hotplug_memory.base = ROUND_UP(machine->ram_size,
> >                                                SPAPR_HOTPLUG_MEM_ALIGN);
> > +
> > +        /* size hotplug region assuming 256M max alignment per slot */
> > +        hotplug_mem_size += SPAPR_MEMORY_BLOCK_SIZE * machine->ram_slots;
> Does target support hugepages backend? If it does then adjustment probably
> should be max supported hugepage alignment.

Hrm, so the maximum possible page size on Power is 16G (though we
don't yet support that on "powernv" which is what the host system will
generally be).

Not sure if the possibility of 16G "colossal pages" in future is
enough reason to put such a huge gap.  There aren't any other page
sizes between 16MB and 16GB.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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