Re: [Xen-devel] [PATCH] x86: avoid HPET use on certain Intel platforms

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.11.2019 13:58, Andrew Cooper wrote:
> On 22/11/2019 12:57, Jan Beulich wrote:
>> On 22.11.2019 13:50, Andrew Cooper wrote:
>>> On 22/11/2019 12:46, Jan Beulich wrote:
>>>> Linux commit fc5db58539b49351e76f19817ed1102bf7c712d0 says
>>>>
>>>> "Some Coffee Lake platforms have a skewed HPET timer once the SoCs entered
>>>>  PC10, which in consequence marks TSC as unstable because HPET is used as
>>>>  watchdog clocksource for TSC."
>>>>
>>>> Follow this for Xen as well. Looking at its patch context made me notice
>>>> they have a pre-existing quirk for Bay Trail as well. The comment there,
>>>> however, points at a Cherry Trail document. Looking at the datasheets of
>>>> both, there appear to be similar issues, so go beyond Linux'es coverage
>>>> and exclude both. Also key the disable on the PCI IDs of the actual
>>>> affected devices, rather than those of 00:00.0.
>>>>
>>>> Apply the workarounds only when the use of HPET was not explicitly
>>>> requested on the command line and when use of (deep) C-states was not
>>>> disabled.
>>>>
>>>> Adjust a few types in touched or nearby code at the same time.
>>> Reported-by ?
>> The Linux commit has a Suggested-by, but no Reported-by. Do you
>> want me to copy that one? Or else do you have any suggestion as
>> to who the reporter was?
> 
> Well - this patch was identified by someone on xen-devel, which I
> presume was your basis for looking into it.

No, it was me spotting the Linux commit in the stable 5.3 ChangeLog.

Jan

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