Re: [patch 2/2] x86/tsc: Force TSC_ADJUST register to value >= zero
From: Thomas Gleixner
Date: Fri Dec 16 2016 - 06:56:46 EST
On Fri, 16 Dec 2016, Ingo Molnar wrote:
> * Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > We have two options:
> > 1) Disable TSC deadline timer by default and force users with sane machines
> > to enable it on the kernel command line.
> > Upside: Very small patch
> > Downside: Degrades existing setups on sane machines, keeps TSC unusable
> > on affected machines. We have no idea what other hidden side
> > effects the TSC_ADJUST tinkering has. If there are any, they
> > ain't be nice ones.
> > 2) Push the whole TSC_ADJUST sanitizing machinery into stable
> > Upside: Does not affect sane machines and gives a benefit to users of
> > affected machines
> > Downside: Rather large patch, but not that risky either. Needs a few
> > eyes and good test coverage though
> > Thoughts?
> I'd go for #2, because #1 is essentially turning it off for almost everyone.
> We can still do #1 and push it back to -stable as well if #2 fails.
> But I'd suggest we delay the stable backporting until it's been upstream a bit.
I agree. None of these patches is tagged stable. I just wanted to mention
it so it can be discussed before distros/stable users are swamped with