Re: [PATCH] x86: Trust initial offset in architectural TSC-adjust MSRs

[Peter Zijlstra]

On Mon, Feb 26, 2024 at 03:25:33PM +0800, Daniel J Blueman wrote:
> When the BIOS configures the architectural TSC-adjust MSRs on secondary
> sockets to correct a constant inter-chassis offset, after Linux brings
> the cores online, the TSC sync check later resets the core-local MSR to
> 0, triggering HPET fallback and leading to performance loss.
> 
> Fix this by unconditionally using the initial adjust values read from the
> MSRs. Trusting the initial offsets in this architectural mechanism is a
> better approach than special-casing workarounds for specific platforms.

Given the amount of BIOS fail in general, I'm thinking the number of
machines that have multi-chassis and get this right are far less than
the 'small' systems that get this wrong.