Re: [PATCH 3/8] drm/amdgpu: Implement mmap as GEM object function

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On 2021-04-07 3:34 p.m., Felix Kuehling wrote:
On 2021-04-07 7:25 a.m., Christian König wrote:
+    /*
+     * Don't verify access for KFD BOs. They don't have a GEM
+     * object associated with them.
+     */
+    if (bo->kfd_bo)
+        goto out;
Who does the access verification now?
This is somewhat confusing.

I took this check as-is, including the comment, from amdgpu's
verify_access function. The verify_access function was called by
ttm_bo_mmap. It returned 0 and ttm_bo_mmap did the mapping.
This is probably a left-over from when we mapped BOs using /dev/kfd. We
changed this to use /dev/dri/renderD* a long time ago to fix CPU mapping
invalidations on memory evictions. I think we can let GEM do the access
check.

Ok, good to know.

Thomas can you remove the extra handling in a separate prerequisite patch?

If anybody then bisects to this patch we at least know what to do to get it working again.

FWIW, I ran KFDTest test with this shortcut removed on current amd-staging-drm-next + my HMM patch series, and it didn't seem to cause any issues.

Wait, I celebrated too soon. I was running the wrong kernel. I do see some failures where access is being denied. I need to do more debugging to figure out what's causing that.

Regards,
  Felix



Regards,
  Felix



Regards,
Christian.
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