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Message-ID: <1498119678.31581.68.camel@kernel.crashing.org>
Subject: Re: 1M hugepage size being registered on Linux
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>, victora
 <victora@linux.vnet.ibm.com>, alistair@popple.id.au, jk@ozlabs.org
Cc: victora@br.ibm.com, mauricfo@linux.vnet.ibm.com, linuxppc-dev@ozlabs.org
Date: Thu, 22 Jun 2017 03:21:18 -0500
In-Reply-To: <87wp85sk9o.fsf@concordia.ellerman.id.au>
References: <322aa4a1a11ca79008a8c894c12a80d5@linux.vnet.ibm.com>
 <87wp85sk9o.fsf@concordia.ellerman.id.au>
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On Wed, 2017-06-21 at 20:33 +1000, Michael Ellerman wrote:
> victora <victora@linux.vnet.ibm.com> writes:
> 
> > Hi Alistair/Jeremy,
> > 
> > I am working on a bug related to 1M hugepage size being registered on 
> > Linux (Power 8 Baremetal - Garrison).
> 
> Wasn't that caused by a firmware bug?
> 
> > I was checking dmesg and it seems that 1M page size is coming from 
> > firmware to Linux.
> > 
> > [    0.000000] base_shift=20: shift=20, sllp=0x0130, avpnm=0x00000000, 
> > tlbiel=0, penc=2
> > [    1.528867] HugeTLB registered 1 MB page size, pre-allocated 0 pages
> > 
> > Should Linux support this page size?
> 
> Does it work? :)
> 
> The user manual says it's a supported size, but I thought it didn't work
> (in hardware) for some reason.

Right, I thought there was some config bit to switch between 1M and 16M
and that had never been fully verified ? I don't remember the details.