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Date: Fri, 18 Apr 2008 19:49:48 +1000
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Mathieu Desnoyers <compudj@krystal.dyndns.org>
CC: Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>,
       akpm@osdl.org, "H. Peter Anvin" <hpa@zytor.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       "Frank Ch. Eigler" <fche@redhat.com>, linux-kernel@vger.kernel.org,
       Rusty Russell <rusty@rustcorp.com.au>, Zachary Amsden <zach@vmware.com>
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v2)
References: <20080414230344.GA16061@Krystal> <20080414230530.GB16061@Krystal> <20080416130605.GG6304@elte.hu> <20080416151054.GA32456@elte.hu> <48062343.50606@goop.org> <20080418004800.GA7758@Krystal>
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Mathieu Desnoyers wrote:
> * Jeremy Fitzhardinge (jeremy@goop.org) wrote:
>   
>> Ingo Molnar wrote:
>>     
>>> * Ingo Molnar <mingo@elte.hu> wrote:
>>>
>>>   
>>>       
>>>> thanks Mathieu, i've picked this up into x86.git for more testing.
>>>>     
>>>>         
>>> ... but had to drop it due to missing PARAVIRT support which broke the 
>>> build. I guess on paravirt we could just initially define 
>>> INTERRUPT_RETURN_NMI_SAFE to iret, etc.?
>>>       
>> I have not yet implemented Xen's support for paravirtual NMI, so there's no 
>> scope for breaking anything from my perspective.  When I get around to NMI, 
>> I'll work around whatever's there.  I don't know if lguest or VMI has any 
>> guest NMI support.
>>
>>    J
>>
>>     
>
> I wonder if we could simply paravirtualize the popf instruction, which
> seems to be the only one requiring to run in ring 0.

Hm, I'd need to think about it more.  There's more to NMI's than just 
the popf.

    J