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Re: [PATCH v1 1/2] xen/page_alloc: address violation of Rule 14.3
- To: victorm.lira@xxxxxxx, Federico Serafini <federico.serafini@xxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 28 Apr 2025 09:43:42 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 28 Apr 2025 07:43:50 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 26.04.2025 02:00, victorm.lira@xxxxxxx wrote:
> From: Federico Serafini <federico.serafini@xxxxxxxxxxx>
>
> MISRA C Rule 14.3 states that "Controlling expressions shall not be
> invariant".
>
> Add a SAF comment to deviate the rule for build configurations without
> CONFIG_LLC_COLORING enabled.
I was surprised by this supposedly being the only violation. And indeed it
wasn't very hard to find more. For example, we have a number of
"while ( num_online_cpus() > 1 && ... )", which become compile-time
constant (false) when NR_CPUS=1.
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -2038,6 +2038,7 @@ static struct page_info *alloc_color_heap_page(unsigned
> int memflags,
>
> spin_lock(&heap_lock);
>
> + /* SAF-14-safe MISRA C R14.3 condition always false without LLC_COLORING
> */
> for ( i = 0; i < domain_num_llc_colors(d); i++ )
> {
> unsigned long free = free_colored_pages[domain_llc_color(d, i)];
Hmm, this way the deviation applies even when LLC_COLORING=y.
As to the comment wording - looks like we're pretty inconsistent with that
right now. I, for one, don't think the Misra rule needs (re)stating there;
the SAF index points at all the data that's needed if one cares about the
specifics of the deviation.
Jan
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