linuxkpi: add kernel_fpu_begin/kernel_fpu_end

[val_packett.cool]

Summary

With newer AMD GPUs (>=Navi,Renoir) there is FPU context usage in the amdgpu driver.
The kernel_fpu_begin/end implementations in drm did not even allow nested begin-end blocks.
This patch merges a more complete implementation into base as requested by @manu.

The counter algorithm was tested (with the variables still being static) at https://github.com/freebsd/drm-kmod/pull/45
In this version, the variables are moved into the linuxkpi module, the context is allocated with sysinit once, to avoid silly reallocations all over the place.

---

Adding the file into conf/files.ARCH is quite annoying, would it be better to just ifdef the whole linux_fpu.c instead of excluding it from the build for arches that don't have fpu_kern(9)?

---

By the way the PowerPC crowd really should implement fpu_kern(9) already ;)

Test Plan

Ideally, someone should retest base with this patch + drm at https://github.com/myfreeweb/drm-kmod/commit/5c7c900cceb9afbae9559b1054697a1d22ee704d with the new amdgpus.

[daniel.piecebypiece_yahoo.com]

HI, I have a Navi10 card (5700XT) + AMD 5950X.
If that setup is suitable I would give it try ?

How does the test plan look like ?

cheers Daniel

[val_packett.cool]

In D28061#627000, @daniel.piecebypiece_yahoo.com wrote:

How does the test plan look like ?

• ensure you have the latest src tree from https://cgit.freebsd.org/src/ in /usr/src
• apply the patch (e.g. curl -L https://github.com/DankBSD/base/commit/a3648bffd3e40d5bff6d1362c7c101e712ab1baa.patch | git am)
• the usual buildkernel installkernel
• get the gpu drivers from https://github.com/myfreeweb/drm-kmod/tree/5.4-lts-dank (git clone -b 5.4-lts-dank https://github.com/myfreeweb/drm-kmod)
• build (make -j30) and install ([sudo/doas/..] make install) them
• reboot :)

[daniel.piecebypiece_yahoo.com]

> - ensure you have the latest src tree from https://cgit.freebsd.org/src/ in /usr/src

• apply the patch (e.g. curl -L https://github.com/DankBSD/base/commit/a3648bffd3e40d5bff6d1362c7c101e712ab1baa.patch | git am)
• the usual buildkernel installkernel
• get the gpu drivers from https://github.com/myfreeweb/drm-kmod/tree/5.4-lts-dank (git clone -b 5.4-lts-dank https://github.com/myfreeweb/drm-kmod)
• build (make -j30) and install ([sudo/doas/..] make install) them
• reboot :)

Done. It booted and I used it now for about 15 min. without any in the face issue.
Do you need any logs or sth. ?

[val_packett.cool]

In D28061#627019, @daniel.piecebypiece_yahoo.com wrote:

Done. It booted and I used it now for about 15 min. without any in the face issue.
Do you need any logs or sth. ?

Nah, nothing needed. The FPU stuff is used in the initialization process — if the driver loaded, it's good :)

[• hselasky]

Looks good!

[manu]

Thanks, will comit this today.