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xen-devel
[Xen-devel] Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr
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To: |
Arjan van de Ven <arjan@xxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 03 of 36] x86: add memory barriers to wrmsr |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Wed, 25 Jun 2008 14:08:57 -0700 |
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Cc: |
Mark McLoughlin <markmc@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Eduardo Habkost <ehabkost@xxxxxxxxxx>, Stephen Tweedie <sct@xxxxxxxxxx>, x86@xxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx> |
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Wed, 25 Jun 2008 14:09:34 -0700 |
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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. Either way, I don't think there's
any legitimate reason to let the compiler reorder things around a wrmsr,
and it should be an inherent property of the macro, rather than relying
on ad-hoc barriers where it gets used. After all, that's a fairly
accurate reflection of how the micro-architecture treats wrmsr...
J
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