• J
    x86/smp: Fix __max_logical_packages value setup · 7b0501b1
    Jiri Olsa 提交于
    Frank reported kernel panic when he disabled several cores in BIOS
    via following option:
    
      Core Disable Bitmap(Hex)   [0]
    
    with number 0xFFE, which leaves 16 CPUs in system (out of 48).
    
    The kernel panic below goes along with following messages:
    
     smpboot: Max logical packages: 2^M
     smpboot: APIC(0) Converting physical 0 to logical package 0^M
     smpboot: APIC(20) Converting physical 1 to logical package 1^M
     smpboot: APIC(40) Package 2 exceeds logical package map^M
     smpboot: CPU 8 APICId 40 disabled^M
     smpboot: APIC(60) Package 3 exceeds logical package map^M
     smpboot: CPU 12 APICId 60 disabled^M
     ...
     general protection fault: 0000 [#1] SMP^M
     Modules linked in:^M
     CPU: 15 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc5+ #1^M
     Hardware name: SGI UV300/UV300, BIOS SGI UV 300 series BIOS 05/25/2016^M
     task: ffff8801673e0000 ti: ffff8801673ac000 task.ti: ffff8801673ac000^M
     RIP: 0010:[<ffffffff81014d54>]  [<ffffffff81014d54>] uncore_change_context+0xd4/0x180^M
     ...
      [<ffffffff810158ac>] uncore_event_init_cpu+0x6c/0x70^M
      [<ffffffff81d8c91c>] intel_uncore_init+0x1c2/0x2dd^M
      [<ffffffff81d8c75a>] ? uncore_cpu_setup+0x17/0x17^M
      [<ffffffff81002190>] do_one_initcall+0x50/0x190^M
      [<ffffffff810ab193>] ? parse_args+0x293/0x480^M
      [<ffffffff81d87365>] kernel_init_freeable+0x1a5/0x249^M
      [<ffffffff81d86a35>] ? set_debug_rodata+0x12/0x12^M
      [<ffffffff816dc19e>] kernel_init+0xe/0x110^M
      [<ffffffff816e93bf>] ret_from_fork+0x1f/0x40^M
      [<ffffffff816dc190>] ? rest_init+0x80/0x80^M
    
    The reason for the panic is wrong value of __max_logical_packages,
    which lets logical_package_map uninitialized and the uncore code
    relying on this map being properly initialized (maybe we should
    add some safety checks there as well).
    
    The __max_logical_packages is computed as:
    
      DIV_ROUND_UP(total_cpus, ncpus);
      - ncpus being number of cores
    
    With above BIOS setup we get total_cpus == 16 which set
    __max_logical_packages to 2 (ncpus is 12).
    
    Once topology_update_package_map processes CPU with logical
    pkg over 2 we display above messages and fail to initialize
    the physical_to_logical_pkg map, which makes the uncore code
    crash.
    
    The fix is to remove logical_package_map bitmap completely
    and keep and update the logical_packages number instead.
    
    After we enumerate all the present CPUs, we check if the
    enumerated logical packages count is within its computed
    maximum from BIOS data.
    
    If it's not the case, we set this maximum to the new enumerated
    value and freeze any new addition of logical packages.
    
    The freeze is because lot of init code like uncore/rapl/cqm
    depends on having maximum logical package value set to allocate
    their data, so we can't change it later on.
    
    Prarit Bhargava tested the patch and confirms that it solves
    the problem:
    
      From dmidecode:
              Core Count: 24
              Core Enabled: 24
              Thread Count: 48
    
    Orig kernel boot log:
    
     [    0.464981] smpboot: Max logical packages: 19
     [    0.469861] smpboot: APIC(0) Converting physical 0 to logical package 0
     [    0.477261] smpboot: APIC(40) Converting physical 1 to logical package 1
     [    0.484760] smpboot: APIC(80) Converting physical 2 to logical package 2
     [    0.492258] smpboot: APIC(c0) Converting physical 3 to logical package 3
    
    1.  nr_cpus=8, should stop enumerating in package 0:
    
     [    0.533664] smpboot: APIC(0) Converting physical 0 to logical package 0
     [    0.539596] smpboot: Max logical packages: 19
    
    2.  max_cpus=8, should still enumerate all packages:
    
     [    0.526494] smpboot: APIC(0) Converting physical 0 to logical package 0
     [    0.532428] smpboot: APIC(40) Converting physical 1 to logical package 1
     [    0.538456] smpboot: APIC(80) Converting physical 2 to logical package 2
     [    0.544486] smpboot: APIC(c0) Converting physical 3 to logical package 3
     [    0.550524] smpboot: Max logical packages: 19
    
    3.  nr_cpus=49 ( 2 socket + 1 core on 3rd socket), should stop enumerating in
        package 2:
    
     [    0.521378] smpboot: APIC(0) Converting physical 0 to logical package 0
     [    0.527314] smpboot: APIC(40) Converting physical 1 to logical package 1
     [    0.533345] smpboot: APIC(80) Converting physical 2 to logical package 2
     [    0.539368] smpboot: Max logical packages: 19
    
    4.  maxcpus=49, should still enumerate all packages:
    
     [    0.525591] smpboot: APIC(0) Converting physical 0 to logical package 0
     [    0.531525] smpboot: APIC(40) Converting physical 1 to logical package 1
     [    0.537547] smpboot: APIC(80) Converting physical 2 to logical package 2
     [    0.543579] smpboot: APIC(c0) Converting physical 3 to logical package 3
     [    0.549624] smpboot: Max logical packages: 19
    
    5.  kdump (nr_cpus=1) works as well.
    Reported-by: NFrank Ramsay <framsay@redhat.com>
    Tested-by: NPrarit Bhargava <prarit@redhat.com>
    Signed-off-by: NJiri Olsa <jolsa@kernel.org>
    Reviewed-by: NPrarit Bhargava <prarit@redhat.com>
    Acked-by: NPeter Zijlstra <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/20160815101700.GA30090@kravaSigned-off-by: NIngo Molnar <mingo@kernel.org>
    7b0501b1
smpboot.c 41.3 KB