Re: [Xen-devel] [PATCH] xen/include: public: Document the padding in struct xen_hvm_param

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 06/02/2020 15:52, Jan Beulich wrote:
> On 06.02.2020 16:41, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > There is an implicit padding of 2 bytes in struct xen_hvm_param between
> > the field domid and index. Make it explicit by introduce a padding
> > field. This can also serve as documentation.
> >
> > Note that I don't think we can mandate it to be zero because a guest may
> > not have initialized the padding.
> Agreed - we can mandate such only at introduction, not at any
> later time.
>
> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Thank you!

> (I doubt this is the only missing field to make padding explicit.)
Probably not, sadly. I stumbled accross the HVM param implicit padding 
while looking at liveupdating the HVM param.
I guess I could use pahole to check the paddings are explicit for all 
the public structure.
Cheers,

--
Julien Grall

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