RE: [Xen-devel] [PATCH RFC] xen-block: correctly define structuresin public headers

From: Paul Durrant
Date: Tue Dec 03 2013 - 06:07:18 EST


> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of David Vrabel
> Sent: 03 December 2013 11:01
> To: Roger Pau Monne
> Cc: Stefano Stabellini; Julien Grall; linux-kernel@xxxxxxxxxxxxxxx; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; Boris Ostrovsky
> Subject: Re: [Xen-devel] [PATCH RFC] xen-block: correctly define structures
> in public headers
>
> On 03/12/13 10:57, Roger Pau Monne wrote:
> > Using __packed__ on the public interface is not correct, this
> > structures should be compiled using the native ABI, and __packed__
> > should only be used in the backend counterpart of those structures
> > (which needs to handle different ABIs).
> >
> > This was even worse in the ARM case, where the Linux kernel was
> > incorrectly using the X86_32 protocol ABI. This patch fixes it, but
> > also breaks compatibility, so an ARM DomU kernel compiled with
> > this patch will fail to communicate with PV disk devices unless the
> > Dom0 also has this patch.
>
> This ABI change needs to be justified. Why do you think it is
> acceptable to break existing Linux guests? Because I don't think it is.
>

Even if they are lying about their ABI?

Paul

> David
>
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