From: Zhao Liu <zhao1.liu@xxxxxxxxx> The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1]. The main difference between atomic and local mappings is that local mappings doesn't disable page faults or preemption. In drm/i915/gem/i915_gem_phys.c, the functions i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() don't need to disable pagefaults and preemption for mapping because of these 2 reasons: 1. The flush operation is safe for CPU hotplug when preemption is not disabled. In drm/i915/gem/i915_gem_object.c, the functions i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() calls drm_clflush_virt_range() to use CLFLUSHOPT or WBINVD to flush. Since CLFLUSHOPT is global on x86 and WBINVD is called on each cpu in drm_clflush_virt_range(), the flush operation is global and any issue with cpu's being added or removed can be handled safely. 2. Any context switch caused by preemption or sleep (pagefault may cause sleep) doesn't affect the validity of local mapping. Therefore, i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() are two functions where the use of kmap_local_page() in place of kmap_atomic() is correctly suited. 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@xxxxxxxxx Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxx> Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx> Suggested-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> Signed-off-by: Zhao Liu <zhao1.liu@xxxxxxxxx> --- Suggested by credits: Dave: Referred to his explanation about cache flush. Ira: Referred to his task document, review comments and explanation about cache flush. Fabio: Referred to his boiler plate commit message. --- drivers/gpu/drm/i915/gem/i915_gem_phys.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_phys.c b/drivers/gpu/drm/i915/gem/i915_gem_phys.c index 0d0e46dae559..d602ba19ecb2 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_phys.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_phys.c @@ -66,10 +66,10 @@ static int i915_gem_object_get_pages_phys(struct drm_i915_gem_object *obj) if (IS_ERR(page)) goto err_st; - src = kmap_atomic(page); + src = kmap_local_page(page); memcpy(dst, src, PAGE_SIZE); drm_clflush_virt_range(dst, PAGE_SIZE); - kunmap_atomic(src); + kunmap_local(src); put_page(page); dst += PAGE_SIZE; @@ -114,10 +114,10 @@ i915_gem_object_put_pages_phys(struct drm_i915_gem_object *obj, if (IS_ERR(page)) continue; - dst = kmap_atomic(page); + dst = kmap_local_page(page); drm_clflush_virt_range(src, PAGE_SIZE); memcpy(dst, src, PAGE_SIZE); - kunmap_atomic(dst); + kunmap_local(dst); set_page_dirty(page); if (obj->mm.madv == I915_MADV_WILLNEED) -- 2.34.1
