From 1fcb967595a5156da2f081a5ade319c60fc5af72 Mon Sep 17 00:00:00 2001 From: Zhao Liu Date: Sun, 3 Dec 2023 21:29:42 +0800 Subject: drm/i915: Use kmap_local_page() in gem/selftests/huge_pages.c The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1], and this patch converts the call 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 or preemption disables. In drm/i915/gem/selftests/huge_pages.c, function __cpu_check_shmem() mainly uses mapping to flush cache and check the value. There're 2 reasons why __cpu_check_shmem() doesn't need to disable pagefaults and preemption for mapping: 1. The flush operation is safe. Function __cpu_check_shmem() 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. 2. Any context switch caused by preemption or page faults (page fault may cause sleep) doesn't affect the validity of local mapping. Therefore, __cpu_check_shmem() is a function 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@intel.com Suggested-by: Dave Hansen Suggested-by: Ira Weiny Suggested-by: Fabio M. De Francesco Signed-off-by: Zhao Liu Reviewed-by: Ira Weiny Reviewed-by: Fabio M. De Francesco Signed-off-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20231203132947.2328805-5-zhao1.liu@linux.intel.com --- drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/gpu/drm/i915') diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c index 6b9f6cf50bf6..c9e6d77abab0 100644 --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c @@ -1082,7 +1082,7 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, u32 dword, u32 val) goto err_unlock; for (n = 0; n < obj->base.size >> PAGE_SHIFT; ++n) { - u32 *ptr = kmap_atomic(i915_gem_object_get_page(obj, n)); + u32 *ptr = kmap_local_page(i915_gem_object_get_page(obj, n)); if (needs_flush & CLFLUSH_BEFORE) drm_clflush_virt_range(ptr, PAGE_SIZE); @@ -1090,12 +1090,12 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, u32 dword, u32 val) if (ptr[dword] != val) { pr_err("n=%lu ptr[%u]=%u, val=%u\n", n, dword, ptr[dword], val); - kunmap_atomic(ptr); + kunmap_local(ptr); err = -EINVAL; break; } - kunmap_atomic(ptr); + kunmap_local(ptr); } i915_gem_object_finish_access(obj); -- cgit v1.2.3