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 12:43:43 -0700
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To: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Morton <akpm@osdl.org>, Andi Kleen <ak@muc.de>, Chris Wright <chrisw@sous-sol.org>, virtualization@lists.osdl.org, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>
List-Id: virtualization@lists.linuxfoundation.org

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