linux-kernel - Re: [PATCH 1/5] Add a global synchronization point for pvclock

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Message-ID: <4BD212BF.60707@goop.org>
Date:	Fri, 23 Apr 2010 14:35:59 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Zachary Amsden <zamsden@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, Glauber Costa <glommer@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock

On 04/23/2010 02:31 PM, Zachary Amsden wrote:
> Does lfence / mfence actually serialize?  I thought there was some
> great confusion about that not being the case on all AMD processors,
> and possibly not at all on Intel.
>
> A trap, however is a great way to serialize.
>
> I think, there is no serializing instruction which can be used from
> userspace which does not trap, at least, I don't know one off the top
> of my head.

rsm is not technically privileged... but not quite usable from usermode ;)

    J
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