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Date: Tue, 17 Feb 2015 09:30:08 +0530
From: Bharata B Rao <bharata@linux.vnet.ibm.com>
Message-ID: <20150217040008.GA1930@in.ibm.com>
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Subject: Re: [Qemu-devel] [RFC PATCH v1 11/13] spapr: Initialize hotplug
 memory address space
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To: David Gibson <david@gibson.dropbear.id.au>
Cc: imammedo@redhat.com, agraf@suse.de, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com

On Mon, Feb 16, 2015 at 03:56:24PM +1100, David Gibson wrote:
> > > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > > > index ae8b4e1..64681c4 100644
> > > > --- a/include/hw/ppc/spapr.h
> > > > +++ b/include/hw/ppc/spapr.h
> > > > @@ -482,6 +482,9 @@ struct sPAPRTCETable {
> > > >  #define TIMEBASE_FREQ           512000000ULL
> > > >  #define SPAPR_MIN_MEMORY_BLOCK_SIZE (1 << 28) /* 256MB */
> > > >  
> > > > +/* Support a min of 1TB hotplug memory assuming 256MB per slot */
> > > > +#define SPAPR_MAX_RAM_SLOTS     (1ULL << 12)
> > > 
> > > Is this constraint arbitrary, or does it come from something in PAPR+?
> > 
> > Arbitrary max, not defined by PAPR.
> 
> Ok.  Why do we need a fixed maximum value?  I don't see this used to
> size any arrays..

The max slots limit comes from x86 where ACPI limits the max dimm
devices to 256. Since pc-dimm implementation requires this max, I came
up with the above value for ppc.

Regards,
Bharata.