Re: Direct rdtsc call side-effect

Thomas Gleixner
2023-06-01T20:13:35Z

On Thu, Jun 01 2023 at 22:10, Thomas Gleixner wrote:
>
> So back to the options:
>
> 1) Kernel
>
> If at all then this needs to be disabled by default and enabled by
> a command line option along with a big fat warning that it might
> disable TSC for timekeeping and bug reports related to this are
> going to be ignored.
>
> Honestly I'm not too interested in this. It's yet another piece of
> art which needs to be maintained and kept alive for a long time.
>
> The fact that we need to check for synchronized TSCs in the first
> place is hillarious already. TSC_ADJUST makes the resynchronization
> attempt at least halfways sensible.
>
> Without it, it's just a pile of never going to be correct
> heuristics with a flood of "this fixes it for my machine (and
> breaks the rest)" patches.
>
>
> 2) Binary patching
>
> Unfortunately RDTSC is only a two byte instruction, but there are
> enough advanced binary patching tools to deal with that.
>
> It might be a completely crazy idea, but I wouldn't dismiss it
> before trying.

Duh. Hit send too early

3) Virtualization

Obviously not trivial either but definitely workable.

Thanks,

tglx