drm/i915: Use kmap_local_page() in gem/i915_gem_execbuffer.c

The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()[1], and this patch converts the calls from
kmap_atomic() to kmap_local_page().

The main difference between atomic and local mappings is that local
mappings doesn't disable page faults or preemption (the preemption is
disabled for !PREEMPT_RT case, otherwise it only disables migration).

With kmap_local_page(), we can avoid the often unwanted side effect of
unnecessary page faults and preemption disables.

In i915_gem_execbuffer.c, eb->reloc_cache.vaddr is mapped by
kmap_atomic() in eb_relocate_entry(), and is unmapped by
kunmap_atomic() in reloc_cache_reset().

And this mapping/unmapping occurs in two places: one is in
eb_relocate_vma(), and another is in eb_relocate_vma_slow().

The function eb_relocate_vma() or eb_relocate_vma_slow() doesn't
need to disable pagefaults and preemption during the above mapping/
unmapping.

So it can simply use kmap_local_page() / kunmap_local() that can
instead do the mapping / unmapping regardless of the context.

Convert the calls of kmap_atomic() / kunmap_atomic() to
kmap_local_page() / kunmap_local().

[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231203132947.2328805-10-zhao1.liu@linux.intel.com

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index b1aa62dfb155d58a46f4bcde2594e28b327a14c8..12cb2ef8dbd62eaed6dbc54fc0547551fc0dd74c 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1158,7 +1158,7 @@ static void reloc_cache_unmap(struct reloc_cache *cache)
 
        vaddr = unmask_page(cache->vaddr);
        if (cache->vaddr & KMAP)
-               kunmap_atomic(vaddr);
+               kunmap_local(vaddr);
        else
                io_mapping_unmap_atomic((void __iomem *)vaddr);
 }
@@ -1174,7 +1174,7 @@ static void reloc_cache_remap(struct reloc_cache *cache,
        if (cache->vaddr & KMAP) {
                struct page *page = i915_gem_object_get_page(obj, cache->page);
 
-               vaddr = kmap_atomic(page);
+               vaddr = kmap_local_page(page);
                cache->vaddr = unmask_flags(cache->vaddr) |
                        (unsigned long)vaddr;
        } else {
@@ -1204,7 +1204,7 @@ static void reloc_cache_reset(struct reloc_cache *cache, struct i915_execbuffer
                if (cache->vaddr & CLFLUSH_AFTER)
                        mb();
 
-               kunmap_atomic(vaddr);
+               kunmap_local(vaddr);
                i915_gem_object_finish_access(obj);
        } else {
                struct i915_ggtt *ggtt = cache_to_ggtt(cache);
@@ -1236,7 +1236,7 @@ static void *reloc_kmap(struct drm_i915_gem_object *obj,
        struct page *page;
 
        if (cache->vaddr) {
-               kunmap_atomic(unmask_page(cache->vaddr));
+               kunmap_local(unmask_page(cache->vaddr));
        } else {
                unsigned int flushes;
                int err;
@@ -1258,7 +1258,7 @@ static void *reloc_kmap(struct drm_i915_gem_object *obj,
        if (!obj->mm.dirty)
                set_page_dirty(page);
 
-       vaddr = kmap_atomic(page);
+       vaddr = kmap_local_page(page);
        cache->vaddr = unmask_flags(cache->vaddr) | (unsigned long)vaddr;
        cache->page = pageno;