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Differential D35554

linprocfs: Decode tsc_invariant CPU feature
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Authored by dchagin on Jun 22 2022, 11:41 PM.
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Linux Emulation
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rGf56ea6b7d0e1: linprocfs: Decode constant_tsc CPU feature
rG8da00a514e69: linprocfs: Decode constant_tsc CPU feature

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dchagin created this revision.Jun 22 2022, 11:41 PM
Herald added a subscriber: imp. · View Herald TranscriptJun 22 2022, 11:41 PM
dchagin requested review of this revision.Jun 22 2022, 11:41 PM
Harbormaster completed remote builds in B46068: Diff 107263.Jun 22 2022, 11:41 PM
dchagin added a reviewer: Linux Emulation.Jun 22 2022, 11:48 PM
dchagin changed the repository for this revision from rS FreeBSD src repository - subversion to rG FreeBSD src repository.
emaste added a subscriber: emaste.Jun 23 2022, 1:07 AM

does Linux report it like this? I couldn't find "invariant_tsc" in the Linux repo

dchagin added a comment.Jun 23 2022, 10:46 AM
In D35554#806404, @emaste wrote:

does Linux report it like this? I couldn't find "invariant_tsc" in the Linux repo

yep, it should be constant_tsc.
our tsc_is_invariant is the same Linux X86_FEATURE_CONSTANT_TSC (which is syntetic bit in the x86_cap_flags)
x86_cap_flags is generated by mkcapflags.sh abd used by procfs to generate CPU flags.

I think that check for invariant_tsc in the /proc/cpuinfo is a bug in glibc tests suite code.
Glibc call cpuid() in the get_extended_indices() and treats CPUID.80000007H:EDX[8] as INVARIANT_TSC and check that invariant_tsc exists in the /proc/cpuinfo, while it is not exposed by the Linux kernel.

dchagin updated this revision to Diff 107289.Jun 23 2022, 10:54 AM

constant_tsc

Harbormaster completed remote builds in B46091: Diff 107289.Jun 23 2022, 10:54 AM
This revision was not accepted when it landed; it landed in state Needs Review.Jun 29 2022, 7:39 AM
Closed by commit rG8da00a514e69: linprocfs: Decode constant_tsc CPU feature (authored by dchagin). · Explain Why
This revision was automatically updated to reflect the committed changes.
dchagin added a commit: rG8da00a514e69: linprocfs: Decode constant_tsc CPU feature.
dchagin added a commit: rGf56ea6b7d0e1: linprocfs: Decode constant_tsc CPU feature.Jul 13 2022, 11:51 AM

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sys/
compat/
linprocfs/
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sys/compat/linprocfs/linprocfs.c

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