Re: [XEN PATCH 7/7] xen/page_alloc: deviate first_valid_mfn for MISRA C Rule 8.4

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 4 Dec 2023, Nicola Vetrini wrote:
> On 2023-12-04 08:44, Jan Beulich wrote:
> > On 02.12.2023 04:03, Stefano Stabellini wrote:
> > > On Fri, 1 Dec 2023, Jan Beulich wrote:
> > > > On 01.12.2023 03:47, Stefano Stabellini wrote:
> > > > > On Wed, 29 Nov 2023, Nicola Vetrini wrote:
> > > > > > No functional change.
> > > > > > 
> > > > > > Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> > > > > > ---
> > > > > > The preferred way to deviate is to use asmlinkage, but this
> > > > > > modification is only
> > > > > > the consequence of NUMA on ARM (and possibly PPC) being a work in
> > > > > > progress.
> > > > > > As stated in the comment above the textual deviation,
> > > > > > first_valid_mfn will
> > > > > > likely then become static and there would be no need for the comment
> > > > > > anymore.
> > > > > > This works towards having the analysis for this rule clean (i.e. no
> > > > > > violations);
> > > > > > the interest in having a clean rule is that then it could be used to
> > > > > > signal
> > > > > > newly introduced violations by making the analysis job fail.
> > > > > 
> > > > > Please add this text as part of the commit message. It can be done on
> > > > > commit.
> > > > 
> > > > I assume you saw my reply on another of the patches in this series as to
> > > > asmlinkage use on variables? IOW I think this paragraph would also need
> > > > adjustment to account for that.
> > > 
> > > I was going to ask you about that: reading your reply
> > > https://marc.info/?l=xen-devel&m=170142048615336 it is not clear to me
> > > what you are asking or suggesting as next step in regard to asmlinkage
> > > use on variables.
> > 
> > Either we need a separate attribute, or we need affirmation that calling
> > convention attributes are ignored (and going to be going forward) for
> > variables, or we need to resort to SAF-* comments. I'm not sure what's
> > best (assuming the "affirm" wouldn't really be possible).
> > 
> 
> Well, gcc does warn on unsupported attributes for the entity which are being
> dropped. This appears to be the case for calling convention attributes, as
> they are not listed in their documentation for variable attributes, but some
> more digging would be required to determine whether that's always the case.

Given that I don't suppose we have many variables that need deviating
(probably only 2-3 overall?) I think it is just easier to add a SAF
comment.