linux-kernel - Re: [-mm patch] {rd,wr}msr_on

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Message-ID: <20070220002952.GH16332@redhat.com>
Date:	Mon, 19 Feb 2007 19:29:52 -0500
From:	Dave Jones <davej@...hat.com>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...nvz.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [-mm patch] {rd,wr}msr_on_cpu SMP=n optimization

On Tue, Feb 20, 2007 at 01:21:45AM +0100, Adrian Bunk wrote:
 > On Mon, Feb 19, 2007 at 07:14:34PM -0500, Dave Jones wrote:
 > > On Tue, Feb 20, 2007 at 01:07:13AM +0100, Adrian Bunk wrote:
 > >...
 > >  > +#ifdef CONFIG_SMP
 > >  >  void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
 > >  >  void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
 > >  > +#else  /*  CONFIG_SMP  */
 > >  > +static inline void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 > >  > +{
 > >  > +	rdmsr(msr_no, *l, *h);
 > >  > +}
 > >  > +static inline void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
 > >  > +{
 > >  > +	wrmsr(msr_no, l, h);
 > >  > +}
 > >  > +#endif  /*  CONFIG_SMP  */
 > > 
 > > BUG_ON(cpu!=smp_processor_id()) maybe?
 > 
 > This is the CONFIG_SMP=n case.

Yes. If someone is asking for the MSR on a specific CPU in UP mode,
it's a bug.

		Dave

-- 
http://www.codemonkey.org.uk
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