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Message-Id: <1392027794-8643-1-git-send-email-mika.westerberg@linux.intel.com>
Date: Mon, 10 Feb 2014 12:23:13 +0200
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>, Bin Gao <bin.gao@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH v4 1/2] x86, tsc: Fallback to normal calibration if fast MSR calibration fails
From: Thomas Gleixner <tglx@...utronix.de>
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.
Reported-and-tested-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
Thomas, I hope you don't mind that I added your SoB to the patch. It is
after all from you.
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 57ae63cd6ee2..94605c0e9cee 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 19e5adb49a27..6702ee72a38f 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 8b5434f4389f..5dfff5809e74 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;
}
--
1.8.5.2
--
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