Re: [Xen-devel] [PATCH] x86: deal with firmware setting bogus TSC_ADJUST values

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Oct 01, 2018 at 07:42:12AM -0600, Jan Beulich wrote:
> The system Intel have handed me for AVX512 emulator work ("Gigabyte
> Technology Co., Ltd. X299 AORUS Gaming 3 Pro/X299 AORUS Gaming 3
> Pro-CF, BIOS F3 12/28/2017") would not come up under Xen - it hung in
> the middle of Dom0 PCI initialization. As it turned out, Xen's time
> management did not work because of the firmware setting (only) the boot
> CPU's TSC_ADJUST MSR to a large negative value (on the order of -2^50).
> 
> Follow Linux (also shamelessly stealing their comments) in

Is there a specific commit or a range of commits in Linux that you can
put here?

> - clearing the register for the boot CPU (we don't have a need for
>   exceptions here yet, as the only exception in Linux is a class of
>   systems Xen doesn't work on anyway as far as I'm aware),
> - forcing non-negative values uniformly,
> - syncing the registers within sockets.
> Linux caps at 0x7fffffff as well, but their comment saying "as those
> wreckage the timer as well" does, to me at least, neither really explain

I tried to pin down what Linux does by searching the comment here but
nothing showed up -- searching "wreckage" on Linux master only yielded
three results, none of which matched the one you wrote here.

Wei.

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