Re: [PATCH v7 09/12] xen: add runtime parameter access support to hypfs

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.04.2020 11:29, Julien Grall wrote:
> On 03/04/2020 16:31, Jürgen Groß wrote:
>> On 03.04.20 16:51, Jan Beulich wrote:
>>> On 02.04.2020 17:46, Juergen Gross wrote:
>>>> V7:
>>>> - fine tune some parameter initializations (Jan Beulich)
>>>> - call custom_runtime_set_var() after updating the value
>>>> - modify alignment in Arm linker script to 4 (Jan Beulich)
>>>
>>> I didn't ask for this to be unilaterally 4 - I don't think this
>>> would work on Arm64, seeing that there are pointers inside the
>>> struct. This wants to be pointer size, i.e. 4 for Arm32 but 8
>>> for Arm64.
> 
> We don't allow unaligned access on Arm32, so if your structure happen to have 
> a 64-bit value in it then you will get a crash at runtime.
> 
> For safety, it should neither be POINTER_ALIGN or 4, but 8.
> This is going to make your linker more robust.

Would you mind explaining to me why POINTER_ALIGN would be wrong
when the most strictly aligned field in a structure is a pointer?

Jan