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SubjectRe: [PATCH -v2] x86, acpi: Handle xapic/x2apic entries in MADT at same time

* Yinghai Lu <yinghai@kernel.org> wrote:

>
> One system have mixing xapic and x2apic entries in MADT and SRAT.
> BIOS guys insist that ACPI 4.0 SPEC said so, if apic id < 255, even
> the cpus are with x2apic mode pre-enabled, still need to use xapic entries
> instead of x2apic entries.
>
> on 8 socket system with x2apic pre-enabled, will get out of order sequence:
> CPU0: socket0, core0, thread0.
> CPU1 - CPU 40: socket 4 - socket 7, thread 0
> CPU41 - CPU 80: socket 4 - socket 7, thread 1
> CPU81 - CPU 119: socket 0 - socket 3, thread 0
> CPU120 - CPU 159: socket 0 - socket 3, thread 1
>
> so max_cpus=80 will not get all thread0 now.
>
> Need to handle every entry in MADT at same time with xapic and x2apic.
> so we can honor sequence in MADT.
>
> We can use max_cpus= command line to use thread0 in every core,
> because recent MADT always have all thread0 at first.
> Also it could make the cpu to node mapping more sane.
>
> after patch will get
> CPU0 - CPU 79: socket 0 - socket 7, thread 0
> CPU80 - CPU 159: socket 0 - socket 7, thread 1
>
> -v2: update some comments, and change to pass array pointer.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
> arch/x86/kernel/acpi/boot.c | 30 ++++++++++++++++-------
> drivers/acpi/numa.c | 16 +++++++++---
> drivers/acpi/tables.c | 57 +++++++++++++++++++++++++++++++++-----------
> include/linux/acpi.h | 9 ++++++
> 4 files changed, 86 insertions(+), 26 deletions(-)

Seems useful - we can queue it up and can get it tested in the x86 tree if Len acks
the principle and the ACPI approach.

Thanks,

Ingo


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