From 5f0e030930d715920be4de638084aaf8653867e8 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 19 Feb 2014 13:52:29 +0200 Subject: [PATCH] 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/include/asm/tsc.h | 2 +- arch/x86/kernel/tsc.c | 7 ++----- arch/x86/kernel/tsc_msr.c | 28 ++++++++++++++-------------- 3 files changed, 17 insertions(+), 20 deletions(-) diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 57ae63cd6ee..94605c0e9ce 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -66,6 +66,6 @@ extern void tsc_save_sched_clock_state(void); extern void tsc_restore_sched_clock_state(void); /* MSR based TSC calibration for Intel Atom SoC platforms */ -int try_msr_calibrate_tsc(unsigned long *fast_calibrate); +unsigned long try_msr_calibrate_tsc(void); #endif /* _ASM_X86_TSC_H */ diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index acb3b606613..cfbe99f8883 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(); diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c index 8b5434f4389..5dfff5809e7 100644 --- a/arch/x86/kernel/tsc_msr.c +++ b/arch/x86/kernel/tsc_msr.c @@ -77,21 +77,18 @@ static int match_cpu(u8 family, u8 model) /* * Do MSR calibration only for known/supported CPUs. - * Return values: - * -1: CPU is unknown/unsupported for MSR based calibration - * 0: CPU is known/supported, but calibration failed - * 1: CPU is known/supported, and calibration succeeded + * + * Returns the calibration value or 0 if MSR calibration failed. */ -int try_msr_calibrate_tsc(unsigned long *fast_calibrate) +unsigned long try_msr_calibrate_tsc(void) { - int cpu_index; u32 lo, hi, ratio, freq_id, freq; + unsigned long res; + int cpu_index; cpu_index = match_cpu(boot_cpu_data.x86, boot_cpu_data.x86_model); if (cpu_index < 0) - return -1; - - *fast_calibrate = 0; + return 0; if (freq_desc_tables[cpu_index].msr_plat) { rdmsr(MSR_PLATFORM_INFO, lo, hi); @@ -103,7 +100,7 @@ int try_msr_calibrate_tsc(unsigned long *fast_calibrate) pr_info("Maximum core-clock to bus-clock ratio: 0x%x\n", ratio); if (!ratio) - return 0; + goto fail; /* Get FSB FREQ ID */ rdmsr(MSR_FSB_FREQ, lo, hi); @@ -112,16 +109,19 @@ int try_msr_calibrate_tsc(unsigned long *fast_calibrate) pr_info("Resolved frequency ID: %u, frequency: %u KHz\n", freq_id, freq); if (!freq) - return 0; + goto fail; /* TSC frequency = maximum resolved freq * maximum resolved bus ratio */ - *fast_calibrate = freq * ratio; - pr_info("TSC runs at %lu KHz\n", *fast_calibrate); + res = freq * ratio; + pr_info("TSC runs at %lu KHz\n", res); #ifdef CONFIG_X86_LOCAL_APIC lapic_timer_frequency = (freq * 1000) / HZ; pr_info("lapic_timer_frequency = %d\n", lapic_timer_frequency); #endif + return res; - return 1; +fail: + pr_warn("Fast TSC calibration using MSR failed\n"); + return 0; } -- 2.41.0