Re: [PATCH 1/2] x86/IO-APIC: drop setup_ioapic_ids_from_mpc()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.09.2025 15:26, Andrew Cooper wrote:
> On 03/09/2025 8:55 am, Jan Beulich wrote:
>> Along the lines of what b89f8f054f96 ("x86/apic: Drop sync_Arb_IDs()")
>> said, the function is dead logic as well: All 64-bit capable Intel systems
>> have (at least) xAPIC (if not x2APIC).
>>
>> Even if Eclair can't know it, such code is violating Misra rule 2.2 (dead
>> code; we didn't accept that yet, but - where possible - we probably would
>> better follow it). Depending on one's reading, this code may actually be a
>> violation of rule 2.1 (unreachable), which we did accept:
>>
>> "Code is unreachable if, ..., there is no combination of program inputs
>>  that can cause it to be executed."
>>
>> Otoh it's "only" __init code.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> The code change is fine, but the commit message should be first
> paragraph only.
> 
> The first paragraph is plenty of justification to make the change,
> irrespective of anything else.

Well. I wouldn't have added the other parts if we weren't where we are in
the release cycle. Strictly speaking, with them dropped I can't put these
two patches in right now. Oleksii, may I ask for your view please (on
both of the patches, as they're both similar in this regard)?

> The other 3 paragraphs are musings on an area of MISRA where which is
> unclear, or even disputed.  The code here is statically reachable,
> dynamically unreachable, and trying to argue this in terms of dead or
> unreachability detracts from an otherwise clear patch.
> 
> With a very strong preference to have the commit message be only the
> first paragraph, Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Thanks (also for the one for patch 2).

Jan