From 5f0e030930d715920be4de638084aaf8653867e8 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 19 Feb 2014 13:52:29 +0200 Subject: x86, tsc: Fallback to normal calibration if fast MSR calibration fails 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:[] [] 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: [] clockevents_config_and_register+0x20/0x30 [] setup_APIC_timer+0xc8/0xd0 [] setup_boot_APIC_clock+0x4cc/0x4d8 [] native_smp_prepare_cpus+0x3dd/0x3f0 [] kernel_init_freeable+0xc3/0x205 [] ? rest_init+0x90/0x90 [] kernel_init+0xe/0x120 [] ret_from_fork+0x7c/0xb0 [] ? 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: Mika Westerberg Signed-off-by: Thomas Gleixner Cc: Bin Gao Cc: One Thousand Gnomes Cc: Ingo Molnar Cc: H. Peter Anvin Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.com Signed-off-by: Mika Westerberg Signed-off-by: Thomas Gleixner --- arch/x86/kernel/tsc.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'arch/x86/kernel/tsc.c') diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index acb3b606613e..cfbe99f88830 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -653,13 +653,10 @@ unsigned long native_calibrate_tsc(void) /* Calibrate TSC using MSR for Intel Atom SoCs */ local_irq_save(flags); - i = try_msr_calibrate_tsc(&fast_calibrate); + fast_calibrate = try_msr_calibrate_tsc(); local_irq_restore(flags); - if (i >= 0) { - if (i == 0) - pr_warn("Fast TSC calibration using MSR failed\n"); + if (fast_calibrate) return fast_calibrate; - } local_irq_save(flags); fast_calibrate = quick_pit_calibrate(); -- cgit v1.2.1