From: John Levon <levon@movementarian.org>
To: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>
Cc: xen-devel@lists.xensource.com, Jan Beulich <jbeulich@novell.com>
Subject: Re: [PATCH] shared_info size and padding fixes
Date: Thu, 10 Aug 2006 14:34:01 +0100 [thread overview]
Message-ID: <20060810133401.GA26023@totally.trollied.org> (raw)
In-Reply-To: <C100F345.BBF%Keir.Fraser@cl.cam.ac.uk>
On Thu, Aug 10, 2006 at 02:29:25PM +0100, Keir Fraser wrote:
> > No, see the previous discussion with Keir - changing the size of the
> > shared info structure is apparently not part of the ABI (hence the
> > reason for the patch and the explanation above!)
> >
> > Personally this seems unusual at best to me, but that's the way it is,
> > and furthermore has already happened with "nmi_reason".
>
> Your patch looked fine, by the way, except that adding padding to every
> arch-specific portion of shared info seems unnecessary.
Imagine we want to add a new field to shared_info. It has to go after
the "arch" member, or offsets break. Once this happens, none of the
arch_shared_info's can be modified at all, as this will break the offset
of the new member.
It seems vastly better to provide some headroom *now* than to make a
mistake later.
regards
john
next prev parent reply other threads:[~2006-08-10 13:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-09 21:05 [PATCH] shared_info size and padding fixes John Levon
2006-08-10 8:03 ` Tristan Gingold
2006-08-10 8:31 ` Jan Beulich
2006-08-10 8:42 ` Tristan Gingold
2006-08-10 8:33 ` Jan Beulich
2006-08-10 12:13 ` John Levon
2006-08-10 13:29 ` Keir Fraser
2006-08-10 13:34 ` John Levon [this message]
2006-08-11 13:30 ` John Levon
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