x86: Add routines for querying XSAVE feature information
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Authored by bnovkov on Fri, Nov 1, 3:28 PM.

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br
kib

Summary

This patch adds several routines that track and expose information about various XSAVE-related features.
More specifically, it adds the ability to check whether a given XFEATURE is supported and which XSAVE extensions are supported.
Furthermore, it adds several routines for calculating the size and offsets within a save area given a XSAVE feature bitmap.

Test Plan

Tested by converting D46397 to use the newly added interfaces.
No issues were encountered while tracing.

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rG FreeBSD src repository

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Event Timeline

bnovkov created this revision.Fri, Nov 1, 3:28 PM

Herald added a subscriber: imp. · View Herald TranscriptFri, Nov 1, 3:28 PM

bnovkov requested review of this revision.Fri, Nov 1, 3:28 PM

bnovkov added a child revision: D46397: amd64: Intel Processor Trace support.

A quick remark regarding code placement - I couldn't decide where this code should reside so I ultimately placed it in cpu_machdep.c, but I'm not too happy about it.
I'd certainly like to hear your thoughts on where this should reside.

amd64/amd64/fpu.c seems to be the natural place for the new functions.
Despite named 'fpu', the file deals with the whole non-GPR part of the CPU state.

sys/x86/include/specialreg.h
381	Commit this chunk already
sys/x86/x86/cpu_machdep.c
1811	Does it ever make sense to call these functions if XSAVE(S) are not supported? Would it be better to convert the checks into KASSERTs?
1817	'else' is not needed