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Date: Mon, 15 Jun 2015 10:15:09 +0200
From: Thomas Huth <thuth@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 5/8] spapr: Consolidate cpu init code
	into a routine
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To: David Gibson <david@gibson.dropbear.id.au>
Cc: qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com, agraf@suse.de, aik@ozlabs.ru, qemu-ppc@nongnu.org, tyreld@linux.vnet.ibm.com, Bharata B Rao <bharata@linux.vnet.ibm.com>, nfont@linux.vnet.ibm.com

On Mon, 15 Jun 2015 16:59:08 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Fri, Jun 05, 2015 at 09:55:55AM +0530, Bharata B Rao wrote:
> > Factor out bits of sPAPR specific CPU initialization code into
> > a separate routine so that it can be called from CPU hotplug
> > path too.
> > 
> > While at this, use MSR_EP define instead of using 6 directly.
> 
> Don't do this please.  MSR[EP] is an obsolete flag from 601.  The
> MSR[IP] flag that we're controlling here just happened to re-use the
> same bit position, so using the existing MSR_EP define is misleading.

Actually, I had the same discussion with Bharata already some weeks ago:

http://lists.gnu.org/archive/html/qemu-ppc/2015-05/msg00133.html

> A symbolic name is good, but you should create a new one for MSR[IP]
> instead.

... and I had to realize that IP = EP. IP likely stands for "interrupt
prefix" (I guess), and EP simply means "exception prefix", so just two
words for the same meaning. It's just the "on 601" comment in QEMU that
is completely misleading. So IMHO it should be fine to keep the
"MSR_EP" here (and maybe update the comment in cpu.h with a separate
patch?).

 Thomas