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 10:54:17 +1000 [thread overview]
Message-ID: <1341968057.18850.21.camel@pasglop> (raw)
In-Reply-To: <4FFCCD2D.20407@freescale.com>
On Tue, 2012-07-10 at 19:47 -0500, Scott Wood wrote:
> On 07/10/2012 07:44 PM, Alexander Graf wrote:
> >
> > On 11.07.2012, at 02:34, Scott Wood wrote:
> >> +#ifdef CONFIG_BOOKE
> >> + /*
> >> + * We're not changing address space on Book E, and the extra rfi
> >> + * can hurt when virtualized without hardware support -- whereas
> >> + * mtmsr can be paravirtualized.
> >
> > We can always paravirtualize RFI as well if it makes sense.
>
> I'm not sure that's possible. We thought about it a while back, but
> IIRC the difficulty was not leaving a register clobbered.
Besides mtmsr is slow on real HW as well. Also paravirt as done today
for complex instructions like mtmsr is racy :-) (I already had a chat
about that with Alex a while back, we might want to re-consider what
kind of fix can be done at some point).
Cheers,
Ben.
prev parent reply other threads:[~2012-07-11 0:54 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
2012-07-11 0:44 ` Alexander Graf
2012-07-11 0:47 ` Scott Wood
2012-07-11 0:54 ` Benjamin Herrenschmidt [this message]
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