Re: [PATCH 0/2] RFC: Precise TSC migration

From: Thomas Gleixner
Date: Tue Dec 01 2020 - 08:49:10 EST


On Mon, Nov 30 2020 at 16:16, Marcelo Tosatti wrote:
>> Besides, Linux guests don't sync the TSC via IA32_TSC write,
>> but rather use IA32_TSC_ADJUST which currently doesn't participate
>> in the tsc sync heruistics.
>
> Linux should not try to sync the TSC with IA32_TSC_ADJUST. It expects
> the BIOS to boot with synced TSCs.

That's wishful thinking.

Reality is that BIOS tinkerers fail to get it right. TSC_ADJUST allows
us to undo the wreckage they create.

Thanks,

tglx