[PATCH v5 0/3] x86, apic, kexec: Add disable_cpu_apic kernel parameter

[HATAYAMA Daisuke]

This patch set is to allow kdump 2nd kernel to wake up multiple CPUs
even if 1st kernel crashs on some AP, a continueing work from:

  [PATCH v3 0/2] x86, apic, kdump: Disable BSP if boot cpu is AP
  https://lkml.org/lkml/2013/10/16/300.

At v4, basic design has changed. Now users need to figure out initial
APIC ID of BSP in the 1st kernel and configures kernel parameter for
the 2nd kernel manually using disable_cpu_apic kernel parameter to be
newly introduced in this patch set. This design is more flexible than
the previous version in that we no longer have to rely on ACPI/MP
table to get initial APIC ID of BSP.

Sorry, this patch set have not include in-source documentation
requested by Borislav Petkov yet, but I'll post it later separately,
which would be better to focus on documentation reviewing.

ChangeLog

v4 => v5)

- Rebased on top of v3.12

- Introduce bsp_physical_apicid that has the initial APIC ID for the
  processor with BSP flag on IA32_APIC_BASE MSR. Without this,
  boot_cpu_physical_apicid has temporarilly the value around MP table
  related codes, although it's designed to have the initial APIC ID
  for the processor that is doing the boot up. Use the
  bsp_physical_apicid in MP table related codes; no impact on
  semantics at runtime there.

v3 => v4)

- Rebased on top of v3.12-rc6

- Basic design has been changed. Now users need to figure out initial
  APIC ID of BSP in the 1st kernel and configures kernel parameter for
  the 2nd kernel manually using disable_cpu_apic kernel parameter to
  be newly introduced in this patch set. This design is more flexible
  than the previous version in that we no longer have to rely on
  ACPI/MP table to get initial APIC ID of BSP.

v2 => v3)

- Change default value of boot_cpu_is_bsp to true.

- Before executing rdmsr(MSR_IA32_APICBASE), check if the number of
  processor family is larger than or equal to 6 in order to avoid
  invalid opcode exception on processors where MSR_IA32_APICBASE is
  not supported.

v1 => v2)

- Rebased on top of v3.12-rc5.

- Fix linking time error of boot_cpu_is_bsp_init() in case of
  CONFIG_LOCAL_APIC disabled by adding empty static inline function
  instead.

- Fix missing feature check by means of cpu_has_apic macro in
  boot_cpu_is_bsp_init() before calling rdmsr_safe(MSR_IA32_APICBASE).

  NOTE: I've checked local apic-present case only; I don't have any
  x86 processor without local apic.

- Add __init annotation to boot_cpu_is_bsp_init().

Test

- built with and without CONFIG_LOCAL_APIC, CONFIG_SMP and CONFIG_X86_UP_APIC.
- tested x86_64 in case of acpi and MP table
- tested disable_cpu_apicid=<n> to disable both AP and BSP

---

HATAYAMA Daisuke (3):
      x86, apic: add bsp_physical_apicid
      x86, apic: Add disable_cpu_apicid kernel parameter
      Documentation, x86, apic, kexec: Add disable_cpu_apicid kernel parameter


 Documentation/kernel-parameters.txt    |    9 +++++++
 arch/x86/include/asm/mpspec.h          |    7 +++++
 arch/x86/kernel/apic/apic.c            |   44 ++++++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/common.c           |    5 +++-
 arch/x86/kernel/mpparse.c              |    3 +-
 arch/x86/kernel/setup.c                |    2 +
 arch/x86/mm/amdtopology.c              |    6 ++--
 arch/x86/platform/visws/visws_quirks.c |    6 +++-
 8 files changed, 75 insertions(+), 7 deletions(-)

-- 

Thanks.
HATAYAMA, Daisuke