Re: [XEN PATCH 3/9] x86/smp: drop x86_cpu_to_apicid, use cpu_data[cpu].apicid instead

[Krystian Hebel <krystian.hebel@xxxxxxxxx>]

On 8.02.2024 08:29, Jan Beulich wrote:
> On 14.11.2023 18:50, Krystian Hebel wrote:
> > Both fields held the same data.
> Supposedly the same data only. They come from different origins, and you're
> hiding this quite well by leaving all sites in place where the field is
> written. Both items are also used for entirely separate purposes. So you
> need to
> - explain why both sources of information necessarily provide the same
>    data,
> - especially if there's remaining concern from the above explanation that
>    the two values might end up different in corner cases (running
>    virtualized ourselves comes to mind as a possible example), explain why
>    nevertheless it is fine (risk free) to use the consolidated item for
>    all of the originally separate purposes,
> - either explain or do away with the multiple places setting this single
>    remaining field.
I missed those writes, thanks for pointing this out. I'll have to take
a closer look before deciding what to do with this.
> > --- a/xen/arch/x86/smpboot.c
> > +++ b/xen/arch/x86/smpboot.c
> > @@ -61,10 +61,8 @@ unsigned int __read_mostly nr_sockets;
> >   cpumask_t **__read_mostly socket_cpumask;
> >   static cpumask_t *secondary_socket_cpumask;
> >   
> > -struct cpuinfo_x86 cpu_data[NR_CPUS];
> > -
> > -u32 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
> > -       { [0 ... NR_CPUS-1] = BAD_APICID };
> > +struct cpuinfo_x86 cpu_data[NR_CPUS] =
> > +        { [0 ... NR_CPUS-1] .apicid = BAD_APICID };
> Nit: Stray blank after closing square bracket.
>
> Jan
--
Krystian Hebel
Firmware Engineer
https://3mdeb.com | @3mdeb_com