[Bug 244877] graphics/mesa-dri: Fix vulkan by switching to unsynchronized userptr ioctls

From: <bugzilla-noreply_at_freebsd.org>
Date: Tue, 26 Jul 2022 01:18:23 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244877

--- Comment #12 from Jan Beich <jbeich@FreeBSD.org> ---
(In reply to Ivan from comment #11)
> ioctl(I915_GEM_USERPTR) failed. Try running as root but expect poor stability.

Did you follow this advice (run the app as root)? The workaround in
lang/intel-compute-runtime/files/patch-userptr implements a fallback via a
feature that requires root. Without it running as root would have made no
difference i.e., still failed.

There's no workaround to avoid root. drm-kmod needs to implement
CONFIG_MMU_NOTIFIER but that would be a "fix", not a "workaround".

> Can you enlighten me, should I apply this patch or try something else?

No. attachment 212502 is for Vulkan on Haswell, not OpenCL. Besides,
intel-compute-runtime doesn't support Haswell.

> Workstation uses Skylake CPU, which is rather modern (compared to Broadwell),
> so I suppose it shouldn't use userptr at all, isn't it?

Applies to Vulkan except VK_EXT_external_memory_host. OpenCL in Intel NEO
(compute-runtime) requires userptr, unlike Beignet where userptr was optional
for OpenCL 2.0.

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