Re: [PATCH 7/9] drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c

[Ira Weiny]

On Mon, Oct 17, 2022 at 05:37:23PM +0800, Zhao Liu wrote:
> From: Zhao Liu 
> 
> 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/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.we...@intel.com/T/#u
> 
> Suggested-by: Ira Weiny 

Reviewed-by: Ira Weiny 

> Suggested-by: Fabio M. De Francesco 
> Signed-off-by: Zhao Liu 
> ---
> 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.
> ---
>  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 b91ad4aede1f..64d56f175d32 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> @@ -962,16 +962,13 @@ 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
> 

[PATCH 7/9] drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c

[Zhao Liu]

From: Zhao Liu 

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/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.we...@intel.com/T/#u

Suggested-by: Ira Weiny 
Suggested-by: Fabio M. De Francesco 
Signed-off-by: Zhao Liu 
---
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.
---
 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 b91ad4aede1f..64d56f175d32 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
@@ -962,16 +962,13 @@ 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