linux-kernel - Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

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Message-ID: <20070316092445.GM23174@elte.hu>
Date:	Fri, 16 Mar 2007 10:24:45 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Wrap a set of interesting paravirt_ops calls in a wrapper which makes 
> the callsites available for patching.  Unfortunately this is pretty 
> ugly because there's no way to get gcc to generate a function call, 
> but also wrap just the callsite itself with the necessary labels.
> 
> This patch supports functions with 0-4 arguments, and either void or 
> returning a value.  64-bit arguments must be split into a pair of 
> 32-bit arguments (lower word first).  Small structures are returned in 
> registers.

ugh. This is beyond ugly! Why dont we just compile two images, one for 
Xen and one for native, do two passes to get those two images and 
'merge' them into a single vmlinuz (so that we still have a 'single' 
kernel unit to deal with on the distro side). This way we avoid all this 
crazy, limited, fragile patchery business...

	Ingo
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