RE: [PATCH 2/2] drm/i915/gt: Fix parameter in gmch_ggtt_insert_{entries,page}()

["Yang, Fei" <fei.yang@intel.com>]

> Subject: [PATCH 2/2] drm/i915/gt: Fix parameter in gmch_ggtt_insert_{entries,page}()
>
> When building with clang's -Wincompatible-function-pointer-types-strict,
> the following warnings occur:
>
>   drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c:102:23: error: incompatible function pointer types assigning to 'void (*)(struct i915_address_space *, dma_addr_t, u64, unsigned int, u32)' (aka 'void (*)(struct i915_address_space *, unsigned int, unsigned long long, unsigned int, unsigned int)') from 'void (struct i915_address_space *, dma_addr_t, u64, enum i915_cache_level, u32)' (aka 'void (struct i915_address_space *, unsigned int, unsigned long long, enum i915_cache_level, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict]
>           ggtt->vm.insert_page = gmch_ggtt_insert_page;
>                                ^ ~~~~~~~~~~~~~~~~~~~~~
>   drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c:103:26: error: incompatible function pointer types assigning to 'void (*)(struct i915_address_space *, struct i915_vma_resource *, unsigned int, u32)' (aka 'void (*)(struct i915_address_space *, struct i915_vma_resource *, unsigned int, unsigned int)') from 'void (struct i915_address_space *, struct i915_vma_resource *, enum i915_cache_level, u32)' (aka 'void (struct i915_address_space *, struct i915_vma_resource *, enum i915_cache_level, unsigned int)') [-Werror, -Wincompatible-function-pointer-types-strict]
>           ggtt->vm.insert_entries = gmch_ggtt_insert_entries;
>                                   ^ ~~~~~~~~~~~~~~~~~~~~~~~~
>   2 errors generated.
>
> The warning is pointing out that while 'enum i915_cache_level' and 'unsigned int' are ABI compatible, these indirect calls will fail clang's kernel Control Flow Integrity (kCFI) checks, as the callback's signature does not exactly match the prototype's signature.
>
> To fix this, replace the cache_level parameter with pat_index, as was done in other places within i915 where there is no difference between cache_level and pat_index on certain generations.
>
> Fixes: 9275277d5324 ("drm/i915: use pat_index instead of cache_level")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Fei Yang <fei.yang@intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c b/drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c
> index d6a74ae2527b..866c416afb73 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c
> @@ -18,10 +18,10 @@
>  static void gmch_ggtt_insert_page(struct i915_address_space *vm,
>                                 dma_addr_t addr,
>                                 u64 offset,
> -                               enum i915_cache_level cache_level,
> +                               unsigned int pat_index,
>                                 u32 unused)
>  {
> -     unsigned int flags = (cache_level == I915_CACHE_NONE) ?
> +     unsigned int flags = (pat_index == I915_CACHE_NONE) ?
>               AGP_USER_MEMORY : AGP_USER_CACHED_MEMORY;
>
>       intel_gmch_gtt_insert_page(addr, offset >> PAGE_SHIFT, flags); @@ -29,10 +29,10 @@ static void gmch_ggtt_insert_page(struct i915_address_space *vm,
>
>  static void gmch_ggtt_insert_entries(struct i915_address_space *vm,
>                                    struct i915_vma_resource *vma_res,
> -                                  enum i915_cache_level cache_level,
> +                                  unsigned int pat_index,
>                                    u32 unused)
>  {
> -     unsigned int flags = (cache_level == I915_CACHE_NONE) ?
> +     unsigned int flags = (pat_index == I915_CACHE_NONE) ?
>               AGP_USER_MEMORY : AGP_USER_CACHED_MEMORY;
>
>       intel_gmch_gtt_insert_sg_entries(vma_res->bi.pages, vma_res->start >> PAGE_SHIFT,
>
> --
> 2.40.1