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| author |   Len Brown <len.brown@intel.com> | 2017-12-22 00:27:54 -0500 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2018-01-14 12:14:50 +0100 |
| commit | da4ae6c4a0b8dee5a5377a385545d2250fa8cddb (patch) | |
| tree | 89ea6b232881a8a4238229e08194f33ca841390a /arch/x86/kernel/tsc.c | |
| parent | kdump: Write the correct address of mem_section into vmcoreinfo (diff) | |
| download | linux-dev-da4ae6c4a0b8dee5a5377a385545d2250fa8cddb.tar.xz linux-dev-da4ae6c4a0b8dee5a5377a385545d2250fa8cddb.zip | |
x86/tsc: Future-proof native_calibrate_tsc()
If the crystal frequency cannot be determined via CPUID(15).crystal_khz or
the built-in table then native_calibrate_tsc() will still set the
X86_FEATURE_TSC_KNOWN_FREQ flag which prevents the refined TSC calibration.
As a consequence such systems use cpu_khz for the TSC frequency which is
incorrect when cpu_khz != tsc_khz resulting in time drift.
Return early when the crystal frequency cannot be retrieved without setting
the X86_FEATURE_TSC_KNOWN_FREQ flag. This ensures that the refined TSC
calibration is invoked.
[ tglx: Steam-blastered changelog. Sigh ]
Fixes: 4ca4df0b7eb0 ("x86/tsc: Mark TSC frequency determined by CPUID as known")
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: Bin Gao <bin.gao@intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/0fe2503aa7d7fc69137141fc705541a78101d2b9.1513920414.git.len.brown@intel.com
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 8ea117f8142e..ce4b71119c36 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -612,6 +612,8 @@ unsigned long native_calibrate_tsc(void) } } + if (crystal_khz == 0) + return 0; /* * TSC frequency determined by CPUID is a "hardware reported" * frequency and is the most accurate one so far we have. This |