Messages in this thread Patch in this message | | | From | Zhao Liu <> | Subject | [PATCH v2 7/9] drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c | Date | Wed, 29 Mar 2023 15:32:18 +0800 |
| |
From: Zhao Liu <zhao1.liu@intel.com>
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/gt/uc/intel_us_fw.c, the function intel_uc_fw_copy_rsa() just use the mapping to do memory copy so it doesn't need to disable pagefaults and preemption for mapping. Thus the local mapping without atomic context (not disable pagefaults / preemption) is enough.
Therefore, intel_uc_fw_copy_rsa() is a function where the use of memcpy_from_page() with kmap_local_page() in place of memcpy() with kmap_atomic() is correctly suited.
Convert the calls of memcpy() with kmap_atomic() / kunmap_atomic() to memcpy_from_page() which uses local mapping to copy.
[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/T/#u
v2: No code change since v1, and added description of the motivation of using kmap_local_page().
Suggested-by: Ira Weiny <ira.weiny@intel.com> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Zhao Liu <zhao1.liu@intel.com> --- Suggested by credits: Ira: Referred to his task document and suggestions about using memcpy_from_page() directly. Fabio: Referred to his boiler plate commit message and his description about why kmap_local_page() should be preferred. --- drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c index 65672ff82605..5bbde4abd565 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c @@ -1152,16 +1152,13 @@ size_t intel_uc_fw_copy_rsa(struct intel_uc_fw *uc_fw, void *dst, u32 max_len) for_each_sgt_page(page, iter, uc_fw->obj->mm.pages) { u32 len = min_t(u32, size, PAGE_SIZE - offset); - void *vaddr; if (idx > 0) { idx--; continue; } - vaddr = kmap_atomic(page); - memcpy(dst, vaddr + offset, len); - kunmap_atomic(vaddr); + memcpy_from_page(dst, page, offset, len); offset = 0; dst += len; -- 2.34.1
| |