Use CPUID leaf 0x40000010 for local APIC freq
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Authored by cperciva on Jan 14 2022, 6:32 AM.

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Summary

Some VM systems announce the frequency of the local APIC via the
CPUID leaf 0x40000010. Using this allows us to boot slightly
faster by avoiding the need for timer calibration.

Sponsored by: https://www.patreon.com/cperciva

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Repository

rS FreeBSD src repository - subversion

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Build Status

Buildable 43934
Build 40822: arc lint + arc unit

Event Timeline

cperciva created this revision.Jan 14 2022, 6:32 AM

Herald added a subscriber: imp. · View Herald TranscriptJan 14 2022, 6:32 AM

cperciva requested review of this revision.Jan 14 2022, 6:32 AM

Harbormaster completed remote builds in B43922: Diff 101450.Jan 14 2022, 6:32 AM

cperciva added a parent revision: D33894: TSC: Use 0x40000010 CPUID leaf for all VM types.Jan 14 2022, 6:33 AM

markj added inline comments.Jan 14 2022, 2:58 PM

sys/x86/x86/local_apic.c
1017	Can this multiplication overflow? I suspect `value` should be uint64_t too.

Fix overflow bug

Harbormaster completed remote builds in B43934: Diff 101485.Jan 14 2022, 9:47 PM

cperciva added inline comments.Jan 14 2022, 9:48 PM

sys/x86/x86/local_apic.c
1017	Thanks, fixed!

markj accepted this revision.Jan 14 2022, 11:27 PM

This revision is now accepted and ready to land.Jan 14 2022, 11:27 PM

Committed. (I forgot to include the Differential Revision tag in the commit message.)

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sys/

x86/

local_apic.c

33 lines

Diff 101485

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Use CPUID leaf 0x40000010 for local APIC freqClosedPublicActions