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Date: Thu, 8 Sep 2011 17:50:44 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Jack Steiner <steiner@sgi.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] UV2 - Bug fix for GRU global addresses
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On Thu, 8 Sep 2011 19:29:16 -0500 Jack Steiner <steiner@sgi.com> wrote:

> On Thu, Sep 08, 2011 at 04:51:39PM -0700, Andrew Morton wrote:
> > (cc x86 maintainers)
> > 
> > On Thu, 8 Sep 2011 13:24:13 -0500
> > Jack Steiner <steiner@sgi.com> wrote:
> > 
> > > This patch is a workaround for a UV2 hub bug that affects the format
> > > of system global addresses.
> > > 
> > > The GRU API for UV2 was inadvertently broken by a hardware change. The
> > > format of the physical address used for TLB dropins and for addresses used
> > > with instructions running in unmapped mode has changed. This change was not
> > > documented and became apparent only when diags failed running on system simulators.
> > > 
> > > For UV1, TLB and GRU instruction physical addresses are identical to socket
> > > physical addresses (although high NASID bits must be OR'ed into the
> > > address).
> > > 
> > > For UV2, socket physical addresses need to be converted. The NODE portion of
> > > the physical address needs to be shifted so that the low bit is in bit 39 or
> > > bit 40, depending on an MMR value.
> > > 
> > > It is not yet clear if this bug will be fixed in a silicon respin. If it
> > > is fixed, the hub revision will be incremented & the workaround disabled.
> > 
> > It's unclear to me whether this patch should be merged into 3.1 and/or
> > into 3.0.x and earlier?
> 
> 3.1 is fine. I can push directly to the distros.

Don't do that.  It's better for a pile of reasons for this to come via
kernel.org.

Again, what is the case for backporting?