From mboxrd@z Thu Jan  1 00:00:00 1970
From: Zachary Amsden <zach@vmware.com>
Subject: Re: [PATCH] paravirt.h
Date: Tue, 22 Aug 2006 12:26:46 -0700
Message-ID: <44EB5A76.9060402@vmware.com>
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To: Zachary Amsden <zach@vmware.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arjan van de Ven <arjan@infradead.org>, Andi Kleen <ak@muc.de>, virtualization@lists.osdl.org, Jeremy Fitzhardinge <jeremy@goop.org>, Andrew Morton <akpm@osdl.org>, Chris Wright <chrisw@sous-sol.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
List-Id: virtualization@lists.linuxfoundation.org

Zachary Amsden wrote:

 > I've already implemented the locking and repatching bits for VMI.


Incorrectly, I might add.  The problem case for syscall patching is what 
do you do if there are in-service system calls?  The comparable problem 
here is what if you interrupt code running in the old paravirt-ops, or 
worse, a section of code that you repatch when you do the switch?

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?).

Thanks,

Zach