Re: [PATCH v4 1/3] x86, apic: Don't count the CPU with BP flag fromMP table as booting-up CPU

[HATAYAMA Daisuke]

(2013/11/12 1:52), Vivek Goyal wrote:
> On Mon, Nov 11, 2013 at 11:52:30AM +0900, HATAYAMA Daisuke wrote:
>
> [..]
> > Looking at my past investigation, kernel/mpparse.c, mm/amdtopology.c and
> > platform/visws/visws_quirks.c assumes that boot_cpu_physical_apicid
> > has initial apicid of the BSP, not the current actual booting-up cpu.
> >
> > These three are called in get_smp_config() below. If either of them is
> > called actually, boot_cpu_physical_apicid has the apicid different from
> > the current actual booting-up cpu temporarily. But init_apic_mappings()
> > soon modifies back the value to the one obtained by read_apic_id().
> >
> >          /*
> >           * Read APIC and some other early information from ACPI tables.
> >           */
> >          acpi_boot_init();
> >          sfi_init();
> >          x86_dtb_init();
> >
> >          /*
> >           * get boot-time SMP configuration:
> >           */
> >          if (smp_found_config)
> >                  get_smp_config();
> >
> >          prefill_possible_map();
> >
> >          init_cpu_to_node();
> >
> >          init_apic_mappings();
> >
> > So, thanks to init_apic_mappings(), the patch set would work without the
> > first patch... This is a careless point in this patch set.
>
> If init_apic_mappings(), is making sure that boot_cpu_physical_apicid is
> apic id of booting processor, and you don't need first patch of your
> series, then I think atleast re-post your patch series without first
> patch.

Yes, I'll repost soon.

> And then there can be another series which looks into whether we need
> two different variables or not and if we do, then a separate variable
> bsp_physical_apicid will track the bsp id as reported by BIOS and
> boot_cpu_physical_apicid will track apic id of booting cpu. This might
> a very big and slow cleanup. So I think blocking the first patch series
> behind it might not make much sense.

Yes, the current handling of boot_cpu_physical_apicid looks strange and
should be cleaned up, but the cleaning up needs reviewing together with
the maintainers for the corresponding part; in particular, it can be
lengthy for the reviewing on amdtopology.c. I leave this as another
work for the time being.

--
Thanks.
HATAYAMA, Daisuke

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