[PATCH] drm/ttm: revert "Fix COW check"

[Alex Deucher]

On Fri, Jul 16, 2021 at 3:06 AM Christian König
<ckoenig.leichtzumerken at gmail.com> wrote:
>
> This reverts commit 85fd4a8a84316166640102676a356755ddec80e0.
>
> Daniel pointed out that even PROT_READ can cause a BUG_ON() with this.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>

Acked-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c  |  3 +--
>  drivers/gpu/drm/nouveau/nouveau_gem.c    |  3 +--
>  drivers/gpu/drm/radeon/radeon_gem.c      |  3 +--
>  drivers/gpu/drm/ttm/ttm_bo_vm.c          | 14 +-------------
>  drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c |  1 -
>  include/drm/ttm/ttm_bo_api.h             |  4 ----
>  6 files changed, 4 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 0d65c9d2144e..9cf4beaf646c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -79,8 +79,7 @@ static const struct vm_operations_struct amdgpu_gem_vm_ops = {
>         .fault = amdgpu_gem_fault,
>         .open = ttm_bo_vm_open,
>         .close = ttm_bo_vm_close,
> -       .access = ttm_bo_vm_access,
> -       .mprotect = ttm_bo_vm_mprotect
> +       .access = ttm_bo_vm_access
>  };
>
>  static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index 164ea564bb7a..5b27845075a1 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -70,8 +70,7 @@ static const struct vm_operations_struct nouveau_ttm_vm_ops = {
>         .fault = nouveau_ttm_fault,
>         .open = ttm_bo_vm_open,
>         .close = ttm_bo_vm_close,
> -       .access = ttm_bo_vm_access,
> -       .mprotect = ttm_bo_vm_mprotect
> +       .access = ttm_bo_vm_access
>  };
>
>  void
> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
> index c19ad07eb7b5..458f92a70887 100644
> --- a/drivers/gpu/drm/radeon/radeon_gem.c
> +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> @@ -77,8 +77,7 @@ static const struct vm_operations_struct radeon_gem_vm_ops = {
>         .fault = radeon_gem_fault,
>         .open = ttm_bo_vm_open,
>         .close = ttm_bo_vm_close,
> -       .access = ttm_bo_vm_access,
> -       .mprotect = ttm_bo_vm_mprotect
> +       .access = ttm_bo_vm_access
>  };
>
>  static void radeon_gem_object_free(struct drm_gem_object *gobj)
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index fb325bad5db6..f56be5bc0861 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -542,29 +542,17 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>  }
>  EXPORT_SYMBOL(ttm_bo_vm_access);
>
> -int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
> -                      unsigned long end, unsigned long newflags)
> -{
> -       /* Enforce no COW since would have really strange behavior with it. */
> -       if (is_cow_mapping(newflags) && (newflags & VM_WRITE))
> -               return -EINVAL;
> -
> -       return 0;
> -}
> -EXPORT_SYMBOL(ttm_bo_vm_mprotect);
> -
>  static const struct vm_operations_struct ttm_bo_vm_ops = {
>         .fault = ttm_bo_vm_fault,
>         .open = ttm_bo_vm_open,
>         .close = ttm_bo_vm_close,
>         .access = ttm_bo_vm_access,
> -       .mprotect = ttm_bo_vm_mprotect,
>  };
>
>  int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
>  {
>         /* Enforce no COW since would have really strange behavior with it. */
> -       if (is_cow_mapping(vma->vm_flags) && (vma->vm_flags & VM_WRITE))
> +       if (is_cow_mapping(vma->vm_flags))
>                 return -EINVAL;
>
>         ttm_bo_get(bo);
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> index e4bf7dc99320..e6b1f98ec99f 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> @@ -61,7 +61,6 @@ int vmw_mmap(struct file *filp, struct vm_area_struct *vma)
>                 .fault = vmw_bo_vm_fault,
>                 .open = ttm_bo_vm_open,
>                 .close = ttm_bo_vm_close,
> -               .mprotect = ttm_bo_vm_mprotect,
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>                 .huge_fault = vmw_bo_vm_huge_fault,
>  #endif
> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> index 40eb95875355..f681bbdbc698 100644
> --- a/include/drm/ttm/ttm_bo_api.h
> +++ b/include/drm/ttm/ttm_bo_api.h
> @@ -605,10 +605,6 @@ void ttm_bo_vm_close(struct vm_area_struct *vma);
>
>  int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>                      void *buf, int len, int write);
> -
> -int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
> -                      unsigned long end, unsigned long newflags);
> -
>  bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all);
>
>  vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);
> --
> 2.25.1
>