linux-kernel - Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr

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Message-ID: <4862CF57.1010106@goop.org>
Date:	Wed, 25 Jun 2008 16:05:59 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	x86@...nel.org, xen-devel <xen-devel@...ts.xensource.com>,
	Stephen Tweedie <sct@...hat.com>,
	Eduardo Habkost <ehabkost@...hat.com>,
	Mark McLoughlin <markmc@...hat.com>
Subject: Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr

Arjan van de Ven wrote:
> On Wed, 25 Jun 2008 14:08:57 -0700
> Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>   
>> Arjan van de Ven wrote:
>>     
>>> it's more readable for several of these cases to stick a barrier();
>>> in front and after it to be honest; that makes it more explicit that
>>> these are deliberate compiler barriers rather than "actual" memory
>>> access...
>>>
>>>   
>>>       
>> I suppose, though I would be inclined to put the barriers in the
>> wrmsr macro itself to act as documentation. 
>>     
>
>
> yeah I meant like this:
>
> static inline void native_write_msr(unsigned int msr,
>  				    unsigned low, unsigned high)
> {
> 	barrier();
> 	asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high));
> 	barrier();
> }
>
> or in the same in the thing that calls this.
>
>   

OK, we're in vehement agreement then.

    J

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