Re: [Xen-devel] [PATCH RFC] xen-block: correctly definestructures in public headers

[Jan Beulich]

>>> On 03.12.13 at 12:05, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2013-12-03 at 11:57 +0100, 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 is acceptable IMHO, the ARM ABI is clearly defined and previous
> kernels were simply buggy. The fact that front and backend were
> equivalently buggy and so it happened to work is not an excuse.

But afaics the change is not just to the ARM form of the ABI,
but to x86 (32- and 64-bit) too. And that clearly must not be
altered.

Jan

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