linux-kernel - Re: [patch] paravirt: VDSO page is essential

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Message-Id: <1173101534.26165.44.camel@localhost.localdomain>
Date:	Tue, 06 Mar 2007 00:32:14 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>,
	Andi Kleen <ak@...e.de>
Subject: Re: [patch] paravirt: VDSO page is essential

On Mon, 2007-03-05 at 15:00 +0200, Avi Kivity wrote:
> Ingo Molnar wrote:
> > * Avi Kivity <avi@...ranet.com> wrote:
> > but yes, i agree that the hypervisor should have the ability to patch 
> > the syscall instruction of both the hypervisor interface and of the VDSO 
> > interface. But this wasnt implemented like that, and the #ifdef quirk 
> > just /prevents/ a sane solution like that from ever getting done the 
> > right way.
> >   
> 
> Rusty, shouldn't this be a one-liner?  No need to involve the hypervisor 
> here; the guest can s/syscall/int 80/ on its vdso page like it patches 
> cli and its ilk.

Probably, but this is a red herring: see previous reply.  Andi was a
little overzealous w/ CONFIG_PARAVIRT & COMPAT_VDSO, that's all.

I've never thought of replacing the syscall insn.  I'll see if I can
come up with a good reason to want to 8)

Rusty.

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