Commit-ID: 6c66350d0a482892793b888b07c1177fc6d4b344 Gitweb: https://git.kernel.org/tip/6c66350d0a482892793b888b07c1177fc6d4b344 Author: mike.travis@xxxxxxx <mike.travis@xxxxxxx> AuthorDate: Thu, 12 Oct 2017 11:32:05 -0500 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Mon, 16 Oct 2017 22:50:37 +0200 x86/tsc: Provide a means to disable TSC ART On systems where multiple chassis are reset asynchronously, and thus the TSC counters are started asynchronously, the offset needed to convert to TSC to ART would be different. Disable ART in that case and rely on the TSC counters to supply the accurate time. Signed-off-by: Mike Travis <mike.travis@xxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Dimitri Sivanich <dimitri.sivanich@xxxxxxx> Cc: Russ Anderson <russ.anderson@xxxxxxx> Cc: Andrew Banman <andrew.banman@xxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Bin Gao <bin.gao@xxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20171012163202.289397994@xxxxxxxxxxxxxxxxxxxxxxxxxx --- arch/x86/kernel/tsc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 896dbe3..f1326c0 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -962,10 +962,14 @@ static void detect_art(void) if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF) return; - /* Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required */ + /* + * Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required, + * and the TSC counter resets must not occur asynchronously. + */ if (boot_cpu_has(X86_FEATURE_HYPERVISOR) || !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) || - !boot_cpu_has(X86_FEATURE_TSC_ADJUST)) + !boot_cpu_has(X86_FEATURE_TSC_ADJUST) || + tsc_async_resets) return; cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator, -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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