From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
Cc: linuxppc-dev@lists.ozlabs.org, Alexander Graf <agraf@suse.de>,
Stuart Yoder <stuart.yoder@freescale.com>
Subject: Re: [PATCH] powerpc/booke: Eliminate rfi from exception entry path.
Date: Wed, 11 Jul 2012 10:53:16 +1000 [thread overview]
Message-ID: <1341967996.18850.20.camel@pasglop> (raw)
In-Reply-To: <4FFCCBAD.40504@freescale.com>
On Tue, 2012-07-10 at 19:41 -0500, Scott Wood wrote:
> On 07/10/2012 07:36 PM, Benjamin Herrenschmidt wrote:
> > On Tue, 2012-07-10 at 19:34 -0500, Scott Wood wrote:
> >> Unlike classic, we don't really need the MSR change to be atomic with the
> >> branch. This eliminates a trap as a KVM guest (in the absence of
> >> hardware hypervisor extensions), where mtmsr is paravirtualized but rfi
> >> is not. For a virtualized guest without any paravirtualization, this
> >> eliminates an additional two traps (SRR0/1).
> >
> > In fact, I wonder, what do we write into the MSR at this point that
> > wasn't already in it in BookE ? RI ? I wonder if we could get away
> > without the mtmsr alltogether...
>
> Doesn't EE get set there for some exceptions?
It does, tho arguably it shouldn't in most cases :-) I'm happy to turn a
bunch of these into explicit local_irq_enable() in the C code though
which will turn into a wrteei which is more efficient on BookE.
Cheers,
Ben.
next prev parent reply other threads:[~2012-07-11 0:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-11 0:34 [PATCH] powerpc/booke: Eliminate rfi from exception entry path Scott Wood
2012-07-11 0:36 ` Benjamin Herrenschmidt
2012-07-11 0:41 ` Scott Wood
2012-07-11 0:53 ` Benjamin Herrenschmidt [this message]
2012-07-11 0:44 ` Alexander Graf
2012-07-11 0:47 ` Scott Wood
2012-07-11 0:54 ` Benjamin Herrenschmidt
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