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

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jul 16, 2021 at 09:14:31AM -0400, Alex Deucher wrote:
> On Fri, Jul 16, 2021 at 3:06 AM Christian König
> <ckoenig.leichtzumerken@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@amd.com>
> 
> Acked-by: Alex Deucher <alexander.deucher@amd.com>

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> 
> > ---
> >  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
> >

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch