Re: [PATCH 1/3] x86/tsc: implement tsc=directsync for systems without IA32_TSC_ADJUST

[Thomas Gleixner]

On Mon, Aug 08 2022 at 16:39, Muhammad Usama Anjum wrote:
> From: Steven Noonan <steven@xxxxxxxxxxxxxx>
>
> AMD processors don't implement any mechanism like Intel's
> IA32_TSC_ADJUST MSR to sync the TSC. Instead of just relying on the
> BIOS, TSC can be synced by calculating the difference and directly
> writing it to the TSC MSR.

Why? This has been tried before and is known to be flaky and
unrealiable.

> Add directsync flag to turn on the TSC sync when IA32_TSC_MSR isn't
> available. Attempt 1000 times or for 30 seconds before giving up.

Looping 30 seconds with interrupts disabled? Seriously?

Thanks,

        tglx