linux-kernel - Re: TSC x86 fixes for LTS kernel 4.9.x

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Date:   Wed, 13 Dec 2017 11:45:20 +0200
From:   Dan Aloni <dan@...nelim.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     stable@...r.kernel.org,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bin Gao <bin.gao@...ux.intel.com>
Subject: Re: TSC x86 fixes for LTS kernel 4.9.x

On Wed, Dec 13, 2017 at 10:03:35AM +0100, Greg KH wrote:
> On Wed, Dec 13, 2017 at 10:33:52AM +0200, Dan Aloni wrote:
> > 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:
> > 
[..]
> 
> I need git commit ids to be able to do anything :)

Sure, how about:

# git log 8c9b9d87b855 --oneline -n 19 --reverse --pretty="%h # %s" | awk -F" " '{print "git cherry-pick -x " $0}'

git cherry-pick -x 47c95a46d0fa # x86/tsc: Add X86_FEATURE_TSC_KNOWN_FREQ flag
git cherry-pick -x 4ca4df0b7eb0 # x86/tsc: Mark TSC frequency determined by CPUID as known
git cherry-pick -x 4635fdc696a8 # x86/tsc: Mark Intel ATOM_GOLDMONT TSC reliable
git cherry-pick -x f3a02ecebed7 # x86/tsc: Set TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Atom SoCs
git cherry-pick -x 984fecebda3b # x86/tsc: Finalize the split of the TSC_RELIABLE flag
git cherry-pick -x 7b3d2f6e08ed # x86/tsc: Use X86_FEATURE_TSC_ADJUST in detect_art()
git cherry-pick -x bec8520dca0d # x86/tsc: Detect random warps
git cherry-pick -x 8b223bc7abe0 # x86/tsc: Store and check TSC ADJUST MSR
git cherry-pick -x 1d0095feea59 # x86/tsc: Verify TSC_ADJUST from idle
git cherry-pick -x a36f5136814b # x86/tsc: Sync test only for the first cpu in a package
git cherry-pick -x 4c5e3c637521 # x86/tsc: Move sync cleanup to a safe place
git cherry-pick -x 76d3b8515850 # x86/tsc: Prepare warp test for TSC adjustment
git cherry-pick -x cc4db26899dc # x86/tsc: Try to adjust TSC if sync test fails
git cherry-pick -x b836554386cc # x86/tsc: Fix broken CONFIG_X86_TSC=n build
git cherry-pick -x 31f8a651fc57 # x86/tsc: Validate cpumask pointer before accessing it
git cherry-pick -x 6a369583178d # x86/tsc: Validate TSC_ADJUST after resume
git cherry-pick -x 5bae156241e0 # x86/tsc: Force TSC_ADJUST register to value >= zero
git cherry-pick -x 16588f659257 # x86/tsc: Annotate printouts as firmware bug
git cherry-pick -x 8c9b9d87b855 # x86/tsc: Limit the adjust value further

There's a conflict only in a one small place in the first few patches.

> > 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
> 
> Why not just use 4.14 instead?  That's much easier than trying to use an
> old kernel like 4.9, right?

Yes, however the milage of 4.9.x seems more appealing somewhat.

I'll give 4.14.x a try mostly to see whether it solves hard locks that
I've seen with 4.13.x (all Fedora-based stable kernels) on three of my
machines -- an unrelated issue, and the main reason why I gave one of
the LTS branches a try.

-- 
Dan Aloni