Re: [PATCH][4.15] x86/HPET: don't enable legacy replacement mode unconditionally

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Jan Beulich writes ("[PATCH][4.15] x86/HPET: don't enable legacy replacement 
mode unconditionally"):
> Commit e1de4c196a2e ("x86/timer: Fix boot on Intel systems using ITSSPRC
> static PIT clock gating") was reported to cause boot failures on certain
> AMD Ryzen systems. Until we can figure out what the actual issue there
> is, skip this new part of HPET setup by default. Introduce a "hpet"
> command line option to allow enabling this on hardware where it's really
> needed for Xen to boot successfully (i.e. where the PIT doesn't drive
> the timer interrupt).
> 
> Since it makes little sense to introduce just "hpet=legacy-replacement",
> also allow for a boolean argument as well as "broadcast" to replace the
> separate "hpetbroadcast" option.

Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>

Thanks.  I would like to ee it committed by the end of the week.

I don't feel qualified to review this.  I'm slightly uncomfortable
with the command line rework but I think as you say there probably
isn't a good more-minimal version.

I would like to ask the reviewer(s) to focus on this question: if the
option is not passed, does this revert the behaviour to be identical
to the behaviour of Xen before e1de4c196a2e ?

Thanks,
Ian.