arm: Fix initialization of VFP context
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Authored by kd on Feb 20 2023, 5:40 PM.

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mw
wma
markmi_dsl-only.net
andrew

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rG98c666cf8758: arm: Fix initialization of VFP context

Summary

Make sure that pcb_vfpsaved is always initialized.
Create a vfp_new_thread helper that is heavily based on the arm64 logic.
While here remove un unnecessary assignment and add an assertion to make sure that it's been properly initialized before we return from a VFP exception.

Reported by: Mark Millard <marklmi@yahoo.com>

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kd requested review of this revision.Feb 20 2023, 5:40 PM

kd created this revision.

With the savectx blne -> bl change, D38696.diff, and D38698.diff all applied, all
the activities with all 3 of my small example programs for the armv7 floating
point related problems look to be working just fine: no KASSERT's ( simple_dbl.c
and dbl_and_ull_via_async.cpp activities) and no odd values showing up in a
thread ( dbl_and_ull_multithread.cpp runs for minutes at a time).

andrew added inline comments.Feb 22 2023, 12:44 PM

sys/arm/arm/vm_machdep.c
140–142	Does this work in a kernel config without `VFP`

Fix kernel build when VFP is not used.

sys/arm/arm/vm_machdep.c
140–142	Good find, it does not. I've fixed that in the latest version.

Retesting my 3 armv7 tests based on use of the updates https://reviews.freebsd.org/D38696?id=117780 and https://reviews.freebsd.org/D38698?id=117779 worked fine.

I can confirm that FreeBSD arm32 armv7 is unusable/broken since 6926e2699ae5 and this diff *fixes* it!

Because it is hard to trace down the random errors (eg. neon instructions introduced via zlib/git) it could
save a lot of other peoples headaches (and destroyed git repos) to land this as quick fix for 6926e2699ae5
and discuss the other depending change-sets in review separately.

Thank you!
Michael

@andrew Do you have any more comment w.r.t. this?
If not I'll commit this patch and D38696 soon.

This revision was not accepted when it landed; it landed in state Needs Review.Feb 23 2023, 4:51 PM

Closed by commit rG98c666cf8758: arm: Fix initialization of VFP context (authored by kd). · Explain Why

This revision was automatically updated to reflect the committed changes.

kd added a commit: rG98c666cf8758: arm: Fix initialization of VFP context.

Herald added a subscriber: imp. · View Herald TranscriptFeb 23 2023, 4:51 PM

I did the 3 tests via booting an installed FreeBSD-14.0-CURRENT-arm-armv7-GENERICSD-20230302-005cca8361a4-261233.img.xz (from today) and they all worked fine.

mmel added a subscriber: mmel.Nov 24 2024, 11:55 AM

mmel added inline comments.