linux-kernel - Re: [PATCH 4/8] drm/ttm: factor out ttm_bo_mmap_vma

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Message-ID: <88d5a253-ef9e-c998-6353-5ba8680129f2@suse.de>
Date:   Fri, 13 Sep 2019 15:05:34 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Gerd Hoffmann <kraxel@...hat.com>, dri-devel@...ts.freedesktop.org
Cc:     David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>,
        Huang Rui <ray.huang@....com>,
        Christian Koenig <christian.koenig@....com>
Subject: Re: [PATCH 4/8] drm/ttm: factor out ttm_bo_mmap_vma_setup

Hi

Am 13.09.19 um 14:29 schrieb Gerd Hoffmann:
> Factor out ttm vma setup to a new function.  Reduces
> code duplication a bit and allows to implement
> &drm_gem_object_funcs.mmap in gem ttm helpers.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  include/drm/ttm/ttm_bo_api.h    |  8 ++++++
>  drivers/gpu/drm/ttm/ttm_bo_vm.c | 47 ++++++++++++++++++---------------
>  2 files changed, 33 insertions(+), 22 deletions(-)
> 
> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> index 43c4929a2171..88c652f49602 100644
> --- a/include/drm/ttm/ttm_bo_api.h
> +++ b/include/drm/ttm/ttm_bo_api.h
> @@ -734,6 +734,14 @@ int ttm_fbdev_mmap(struct vm_area_struct *vma, struct ttm_buffer_object *bo);
>  int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
>  		struct ttm_bo_device *bdev);
>  
> +/**
> + * ttm_bo_mmap_vma_setup - initialize vma for ttm bo mmap
> + *
> + * @bo: The buffer object.
> + * @vma: vma as input from the mmap method.
> + */
> +void ttm_bo_mmap_vma_setup(struct ttm_buffer_object *bo, struct vm_area_struct *vma);
> +
>  void *ttm_kmap_atomic_prot(struct page *page, pgprot_t prot);
>  
>  void ttm_kunmap_atomic_prot(void *addr, pgprot_t prot);
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 4aa007edffb0..7c0e85c10e0e 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -426,6 +426,29 @@ static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
>  	return bo;
>  }
>  
> +void ttm_bo_mmap_vma_setup(struct ttm_buffer_object *bo, struct vm_area_struct *vma)
> +{
> +	vma->vm_ops = &ttm_bo_vm_ops;
> +
> +	/*
> +	 * Note: We're transferring the bo reference to
> +	 * vma->vm_private_data here.
> +	 */
> +
> +	vma->vm_private_data = bo;
> +
> +	/*
> +	 * We'd like to use VM_PFNMAP on shared mappings, where
> +	 * (vma->vm_flags & VM_SHARED) != 0, for performance reasons,
> +	 * but for some reason VM_PFNMAP + x86 PAT + write-combine is very
> +	 * bad for performance. Until that has been sorted out, use
> +	 * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719
> +	 */
> +	vma->vm_flags |= VM_MIXEDMAP;
> +	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> +}
> +EXPORT_SYMBOL(ttm_bo_mmap_vma_setup);

To me, this function looks like an internal helper that should rather
remain internal. As mentioned in my reply to patch 5, maybe re-using
ttm_fbdev_mmap() could help.

Best regards
Thomas

> +
>  int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
>  		struct ttm_bo_device *bdev)
>  {
> @@ -449,24 +472,7 @@ int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
>  	if (unlikely(ret != 0))
>  		goto out_unref;
>  
> -	vma->vm_ops = &ttm_bo_vm_ops;
> -
> -	/*
> -	 * Note: We're transferring the bo reference to
> -	 * vma->vm_private_data here.
> -	 */
> -
> -	vma->vm_private_data = bo;
> -
> -	/*
> -	 * We'd like to use VM_PFNMAP on shared mappings, where
> -	 * (vma->vm_flags & VM_SHARED) != 0, for performance reasons,
> -	 * but for some reason VM_PFNMAP + x86 PAT + write-combine is very
> -	 * bad for performance. Until that has been sorted out, use
> -	 * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719
> -	 */
> -	vma->vm_flags |= VM_MIXEDMAP;
> -	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> +	ttm_bo_mmap_vma_setup(bo, vma);
>  	return 0;
>  out_unref:
>  	ttm_bo_put(bo);
> @@ -481,10 +487,7 @@ int ttm_fbdev_mmap(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
>  
>  	ttm_bo_get(bo);
>  
> -	vma->vm_ops = &ttm_bo_vm_ops;
> -	vma->vm_private_data = bo;
> -	vma->vm_flags |= VM_MIXEDMAP;
> -	vma->vm_flags |= VM_IO | VM_DONTEXPAND;
> +	ttm_bo_mmap_vma_setup(bo, vma);
>  	return 0;
>  }
>  EXPORT_SYMBOL(ttm_fbdev_mmap);
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)



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