This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] kexec woes with 32-bit secondary kernel

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] kexec woes with 32-bit secondary kernel
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Fri, 17 Sep 2010 17:57:52 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 17 Sep 2010 09:59:07 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4C93AA320200007800017756@xxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Organization: Citrix Systems, Inc.
References: <4C93AA320200007800017756@xxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Fri, 2010-09-17 at 16:49 +0100, Jan Beulich wrote: 
> Ever since c/s 13829, the native (32-bit -> 32-bit) call to invoke the
> secondary kernel has been missing its fourth argument. Apparently
> this worked out because the respective stack location was non-zero.

Which argument is this? 

> Starting with Linux 2.6.27 (32-bit) and 2.6.30 (64-bit) a new
> argument is being expected by the secondary kernel, and again
> apparently out of pure luck the 64-bit -> 64-bit case still appears
> to work for those of our customers who want to use it.
> The question really is whether this code has ever been tested
> with sufficiently recent kernels in all three variants (32->32, 64->64,
> and 64->32).

It gets pretty regular testing in XenServer and XCP in the
32on64->32native variant. This works at least with the 2.6.27 and 2.6.32
domain 0 kernels used in those two situations.

I can't speak for any testing done elsewhere though. I suspect that
other than what you guys do there isn't that much of it.

> While it seems that putting together a patch to address this
> shouldn't be that difficult, a second question is how we can avoid
> getting into the same situation again when Linux extends the
> protocol again.

I've always thought that the hypercall interface is rather too closely
modelled on internals of a particular implementation from a particular
version of Linux. On the other hand I'm not sure I have any better


Xen-devel mailing list