Date: Wed, 13 Dec 2017 10:33:52 +0200
From: Dan Aloni <dan@kernelim.com>
To: stable@vger.kernel.org
Cc: Linux Kernel List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Bin Gao <bin.gao@linux.intel.com>
Subject: TSC x86 fixes for LTS kernel 4.9.x
Message-ID: <20171213083352.GA15356@gmail.com>
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Hi all,

I've tested the following changes, belonging to merge commit f7dd3b1734e,
on top of 4.9.68 after a very easy backport from 4.10, and I think it
may be worthwhile adding them to 4.9.x:

      x86/tsc: Limit the adjust value further
      x86/tsc: Annotate printouts as firmware bug
      x86/tsc: Force TSC_ADJUST register to value >= zero
      x86/tsc: Validate TSC_ADJUST after resume
      x86/tsc: Validate cpumask pointer before accessing it
      x86/tsc: Fix broken CONFIG_X86_TSC=n build
      x86/tsc: Try to adjust TSC if sync test fails
      x86/tsc: Prepare warp test for TSC adjustment
      x86/tsc: Move sync cleanup to a safe place
      x86/tsc: Sync test only for the first cpu in a package
      x86/tsc: Verify TSC_ADJUST from idle
      x86/tsc: Store and check TSC ADJUST MSR
      x86/tsc: Detect random warps
      x86/tsc: Use X86_FEATURE_TSC_ADJUST in detect_art()
      x86/tsc: Finalize the split of the TSC_RELIABLE flag
      x86/tsc: Set TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Atom SoCs
      x86/tsc: Mark Intel ATOM_GOLDMONT TSC reliable
      x86/tsc: Mark TSC frequency determined by CPUID as known
      x86/tsc: Add X86_FEATURE_TSC_KNOWN_FREQ flag

These changes percisely fix an issue I am having with a relatively new
8-core Intel(R) Core(TM) i7-7820X with an updated ASUS BIOS (December 2017).

Under v4.9.68, the kernel fallbacks on the chosen clocksource to HPET which
just doesn't work - there is over a 200ms time drift that does not go
away even after repeated ntpdate sync attempts.

For further testing I've posted a branch for these changes here:

    https://github.com/kernelim/linux tsc-fix-for-4.9.x

-- 
Dan Aloni