[PATCH v5 0/3] Fix panic in logical packages calculation

[Prarit Bhargava]

A system booted with a small number of cores enabled per package
panics because the estimate of __max_logical_packages is too low.
This occurs when the total number of active cores across all packages
is less than the maximum core count for a single package.

Andi noted that the logical_packages calculation wastes 128k on 64-bit
x86 systems and posted patches to fix the allocation.  His patches
result in significant memory size savings, and I have put my
fix on top of those patches.

Here's an example of the panic:

     smpboot: Booting Node   1, Processors  #1 OK
     smpboot: Package 1 of CPU 1 exceeds BIOS package data 1.
     ------------[ cut here ]------------
     kernel BUG at arch/x86/kernel/cpu/common.c:1087!
     invalid opcode: 0000 [#1] SMP
     Modules linked in:
     CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.14.0-rc2+ #4

This was tested by dropping the number of active cores across
all packages to reproduce the bug above.  Additional testing included
2 socket and 4 socket systems and hotplugging entire sockets in different
order.

Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Piotr Luc <piotr.luc@xxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

Andi Kleen (2):
  perf/x86/intel/uncore: Cache logical pkg id in uncore driver
  x86/topology: Avoid wasting 128k for package id array

Prarit Bhargava (1):
  x86/smpboot: Fix __max_logical_packages estimate

 arch/x86/events/intel/uncore.c       |   1 +
 arch/x86/events/intel/uncore.h       |   1 +
 arch/x86/events/intel/uncore_snbep.c |   2 +-
 arch/x86/kernel/smpboot.c            | 148 ++++++++++++++---------------------
 4 files changed, 61 insertions(+), 91 deletions(-)

-- 
2.15.0.rc0.39.g2f0e14e64