[PATCH v2] drm/i915/gt: Replace kmap with its safer kmap_local_page counterpart

[Gote, Nitin R]

Hi Andi, 

> -----Original Message-----
> From: Andi Shyti <andi.shyti at linux.intel.com>
> Sent: Friday, February 14, 2025 6:05 AM
> To: intel-gfx <intel-gfx at lists.freedesktop.org>; dri-devel <dri-
> devel at lists.freedesktop.org>
> Cc: Andi Shyti <andi.shyti at linux.intel.com>; Karas, Krzysztof
> <krzysztof.karas at intel.com>; Gote, Nitin R <nitin.r.gote at intel.com>
> Subject: [PATCH v2] drm/i915/gt: Replace kmap with its safer kmap_local_page
> counterpart
> 
> kmap_local_page(), unlike kmap(), performs a contextualized mapping of pages.
> This means the pages are mapped locally to the thread that created them, making
> them invisible outside the thread and safer to use.
> 
> Replace kmap() and kunmap() with kmap_local_page() and
> kunmap_local() counterparts for improved safety.
> 
> Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
> Reviewed-by: Krzysztof Karas <krzysztof.karas at intel.com>
> ---
> Cc: Nitin Gote <nitin.r.gote at intel.com>
> 
> v1 -> v2:
>  - replaced kmap with the _local version also in the
>    intel_ggtt_fencing.c file. (Thanks Nitin)
> 
>  drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c | 4 ++--
>  drivers/gpu/drm/i915/gt/shmem_utils.c        | 8 ++++----
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
> b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
> index 0ffba50981e3..00f7cd6debf3 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
> @@ -749,7 +749,7 @@ static void swizzle_page(struct page *page)
>  	char *vaddr;
>  	int i;
> 
> -	vaddr = kmap(page);
> +	vaddr = kmap_local_page(page);
> 
>  	for (i = 0; i < PAGE_SIZE; i += 128) {
>  		memcpy(temp, &vaddr[i], 64);
> @@ -757,7 +757,7 @@ static void swizzle_page(struct page *page)
>  		memcpy(&vaddr[i + 64], temp, 64);
>  	}
> 
> -	kunmap(page);
> +	kunmap_local(vaddr);
>  }
> 
>  /**
> diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c
> b/drivers/gpu/drm/i915/gt/shmem_utils.c
> index bb696b29ee2c..365c4b8b04f4 100644
> --- a/drivers/gpu/drm/i915/gt/shmem_utils.c
> +++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
> @@ -108,7 +108,7 @@ static int __shmem_rw(struct file *file, loff_t off,
>  		if (IS_ERR(page))
>  			return PTR_ERR(page);
> 
> -		vaddr = kmap(page);
> +		vaddr = kmap_local_page(page);
>  		if (write) {
>  			memcpy(vaddr + offset_in_page(off), ptr, this);
>  			set_page_dirty(page);
> @@ -116,7 +116,7 @@ static int __shmem_rw(struct file *file, loff_t off,
>  			memcpy(ptr, vaddr + offset_in_page(off), this);
>  		}
>  		mark_page_accessed(page);
> -		kunmap(page);
> +		kunmap_local(vaddr);
>  		put_page(page);
> 
>  		len -= this;
> @@ -143,11 +143,11 @@ int shmem_read_to_iosys_map(struct file *file, loff_t
> off,
>  		if (IS_ERR(page))
>  			return PTR_ERR(page);
> 
> -		vaddr = kmap(page);
> +		vaddr = kmap_local_page(page);
>  		iosys_map_memcpy_to(map, map_off, vaddr +
> offset_in_page(off),
>  				    this);
>  		mark_page_accessed(page);
> -		kunmap(page);
> +		kunmap_local(vaddr);
>  		put_page(page);
> 
>  		len -= this;
> --
> 2.47.2

LGTM.
Reviewed-by: Nitin Gote <nitin.r.gote at intel.com>