Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1505475

Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag
Date 2016-10-21 07:50 +0200
Message-ID <suASm-1k5-3@gated-at.bofh.it> (permalink)
References (5 earlier) <srmCe-1kH-7@gated-at.bofh.it> <srXs5-1E4-1@gated-at.bofh.it> <suisq-68t-15@gated-at.bofh.it> <suiC5-6ej-1@gated-at.bofh.it> <survH-3sZ-11@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Thu, Oct 20, 2016 at 09:37:50PM +0200, Thomas Gleixner wrote:

> Well, we have the same issue on other platforms/models which set the
> reliable flag.

I was not aware we had other platforms doing this, git grep tells me
intel-mid does this as well..

> So one sanity check we can do is to read the IA32_TSC_ADJUST MSR on all
> cores. They should all have the same value (usually 0) or at least have a
> very minimal delta. If that's off by more than 1us then something is fishy
> especially on single socket systems. We could at least WARN about it.
> 
> We could do this in idle occasionally as well, so we can detect the dreaded
> "SMI wants to hide the cycles" crapola.

Indeed, that sounds like the best we can; and probably should; do.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Bin Gao <bin.gao@linux.intel.com> - 2016-10-14 01:20 +0200
  Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 12:10 +0200
    Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Peter Zijlstra <peterz@infradead.org> - 2016-10-20 12:20 +0200
      Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 21:50 +0200
        Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Peter Zijlstra <peterz@infradead.org> - 2016-10-21 07:50 +0200
          Re: [PATCH v3] x86/tsc: add X86_FEATURE_TSC_KNOWN_FREQ flag Thomas Gleixner <tglx@linutronix.de> - 2016-10-21 10:10 +0200

csiph-web