Differential D21777

x86: Fall back to leaf 0x16 if TSC frequency is obtained by CPUID and leaf 0x15 is not functional.
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Authored by kib on Sep 24 2019, 10:22 AM.

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rS352684: x86: Fall back to leaf 0x16 if TSC frequency is obtained by CPUID and

Summary

This should improve automatic TSC frequency determination on Skylake/Kabylake/... families, where 0x15 exists but does not provide all necessary information. SDM contains relatively strong wording against such uses of 0x16, but Intel does not give us any other way to obtain the frequency. Linux did the same in the commit 604dc9170f2435d27da5039a3efd757dceadc684

Based on submission by: Neel Chauhan <neel@neelc.org>
PR: 240475

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rS FreeBSD src repository - subversion

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Event Timeline

kib created this revision.Sep 24 2019, 10:22 AM

Herald added a subscriber: imp. · View Herald TranscriptSep 24 2019, 10:22 AM

Harbormaster completed remote builds in B26668: Diff 62499.Sep 24 2019, 10:22 AM

markj accepted this revision.Sep 24 2019, 3:17 PM

markj added inline comments.

sys/x86/x86/tsc.c
139 ↗	(On Diff #62499)	"the SDM"
140 ↗	(On Diff #62499)	Should be "did not work".

This revision is now accepted and ready to land.Sep 24 2019, 3:17 PM

Closed by commit rS352684: x86: Fall back to leaf 0x16 if TSC frequency is obtained by CPUID and (authored by kib). · Explain WhySep 25 2019, 1:37 PM

This revision was automatically updated to reflect the committed changes.

kib added a commit: rS352684: x86: Fall back to leaf 0x16 if TSC frequency is obtained by CPUID and.

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sys/

x86/

x86/

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Diff 62543

head/sys/x86/x86/tsc.c

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