• Thomas Gleixner's avatar
    x86, tsc: Fallback to normal calibration if fast MSR calibration fails · 5f0e0309
    Thomas Gleixner authored
    If we cannot calibrate TSC via MSR based calibration
    try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that
    to the caller. This value gets then propagated further to clockevents
    code resulting division by zero oops like the one below:
    
     divide error: 0000 [#1] PREEMPT SMP
     Modules linked in:
     CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W    3.13.0+ #47
     task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000
     RIP: 0010:[<ffffffff810aec14>]  [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0
     RSP: 0000:ffff880075507e58  EFLAGS: 00010246
     RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000
     RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff
     RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be
     R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008
     R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000
     FS:  0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
     CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0
     Stack:
      ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88
      ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168
      ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000
     Call Trace:
      [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30
      [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0
      [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8
      [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0
      [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205
      [<ffffffff8177c910>] ? rest_init+0x90/0x90
      [<ffffffff8177c91e>] kernel_init+0xe/0x120
      [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0
      [<ffffffff8177c910>] ? rest_init+0x90/0x90
    
    Prevent this from happening by:
     1) Modifying try_msr_calibrate_tsc() to return calibration value or zero
        if it fails.
     2) Check this return value in native_calibrate_tsc() and in case of zero
        fallback to use normal non-MSR based calibration.
    
    [mw: Added subject and changelog]
    Reported-and-tested-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Bin Gao <bin.gao@linux.intel.com>
    Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.comSigned-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    5f0e0309
tsc_msr.c 3.38 KB