linux-kernel - Re: [PATCH][KVM][retry 3] Add support for Pause Filtering to AMD SVM

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Message-ID: <4A13C7B0.10507@redhat.com>
Date:	Wed, 20 May 2009 12:04:48 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Mark Langsdorf <mark.langsdorf@....com>,
	Joerg Roedel <joerg.roedel@....com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][KVM][retry 3] Add support for Pause Filtering to AMD
 SVM

Peter Zijlstra wrote:

  

>> It's a fully virtualized guest.  There's no way to get this without 
>> patching the guest kernel.
>>     
>
> Yes there is.. virtualized monitor-wait stuff coupled with a
> monitor-wait based spinlock implementation.
>   

That only works if the guest uses monitor/mwait.  Not all of the guests 
are under our control.  I don't know whether Windows uses 
monitor/mwait.  Further, we don't have timed exits on mwait like we do 
with pause.

I've also heard that monitor/mwait are very slow and only usable on idle 
loop stuff.

> Once we go change silicon, you might as well do it right.
>   

None of the major x86 vendors are under my control.

-- 
error compiling committee.c: too many arguments to function

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