linux-kernel - Re: [PATCH] paravirt.h

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Message-ID: <44EB5E6F.5090001@vmware.com>
Date:	Tue, 22 Aug 2006 12:43:43 -0700
From:	Zachary Amsden <zach@...are.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Andi Kleen <ak@....de>,
	virtualization@...ts.osdl.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...l.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] paravirt.h

Arjan van de Ven wrote:
>> That is a really nasty problem.  You need a synchronization primitive 
>> which guarantees a flat stack, so you can't do it in the interrupt 
>> handler as I have tried to do.  I'll bang my head on it awhile.  In the 
>> meantime, were there ever any solutions to the syscall patching problem 
>> that might lend me a clue as to what to do (or not to do, or impossible?).
>>     
>
> yes we just disallowed it :)
>   

Ok, I just took a cold shower.  Actually, this problem is much easier to 
solve for paravirt-ops, since they are short lived operations and don't 
block.  For syscall, it is much, much harder, since you have syscalls 
that can block forever, so you can't guarantee you'll exit all instances 
of the syscall you want to patch.

I think the paravirt-ops one is doable with exports already provided by 
Linux.

Zach
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