Re: [PATCH v2 1/2] drm/i915: Add i915_gem_object_vmap to map GEM object to virtual space

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 18/02/16 18:31, yu.dai@intel.com wrote:
> From: Alex Dai <yu.dai@intel.com>
>
> There are several places inside driver where a GEM object is mapped to
> kernel virtual space. The mapping is either done for the whole object
> or certain page range of it.
>
> This patch introduces a function i915_gem_object_vmap to do such job.
>
> v2: Use obj->pages->nents for iteration within i915_gem_object_vmap;
>      break when it finishes all desired pages. The caller need to pass
>      in actual page number. (Tvrtko Ursulin)

Look OK to me. Just one more thing, it would be good to add a WARN_ON 
and bail out if pages are not pinned. Just because the function is now 
public and that is a bit stronger than kerneldoc.

With that added:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko


> Signed-off-by: Alex Dai <yu.dai@intel.com>
> Cc: Dave Gordon <david.s.gordon@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Alex Dai <yu.dai@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_cmd_parser.c  | 28 +-------------------
>   drivers/gpu/drm/i915/i915_drv.h         |  3 +++
>   drivers/gpu/drm/i915/i915_gem.c         | 47 +++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/i915_gem_dmabuf.c  | 16 +++--------
>   drivers/gpu/drm/i915/intel_ringbuffer.c | 24 ++---------------
>   5 files changed, 56 insertions(+), 62 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 814d894..915e8c1 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -863,37 +863,11 @@ find_reg(const struct drm_i915_reg_descriptor *table,
>   static u32 *vmap_batch(struct drm_i915_gem_object *obj,
>   		       unsigned start, unsigned len)
>   {
> -	int i;
> -	void *addr = NULL;
> -	struct sg_page_iter sg_iter;
>   	int first_page = start >> PAGE_SHIFT;
>   	int last_page = (len + start + 4095) >> PAGE_SHIFT;
>   	int npages = last_page - first_page;
> -	struct page **pages;
> -
> -	pages = drm_malloc_ab(npages, sizeof(*pages));
> -	if (pages == NULL) {
> -		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
> -		goto finish;
> -	}
> -
> -	i = 0;
> -	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first_page) {
> -		pages[i++] = sg_page_iter_page(&sg_iter);
> -		if (i == npages)
> -			break;
> -	}
> -
> -	addr = vmap(pages, i, 0, PAGE_KERNEL);
> -	if (addr == NULL) {
> -		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
> -		goto finish;
> -	}
>
> -finish:
> -	if (pages)
> -		drm_free_large(pages);
> -	return (u32*)addr;
> +	return (u32*)i915_gem_object_vmap(obj, first_page, npages);
>   }
>
>   /* Returns a vmap'd pointer to dest_obj, which the caller must unmap */
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 6644c2e..5b00a6a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2899,6 +2899,9 @@ struct drm_i915_gem_object *i915_gem_object_create_from_data(
>   		struct drm_device *dev, const void *data, size_t size);
>   void i915_gem_free_object(struct drm_gem_object *obj);
>   void i915_gem_vma_destroy(struct i915_vma *vma);
> +void *i915_gem_object_vmap(struct drm_i915_gem_object *obj,
> +			   unsigned int first,
> +			   unsigned int npages);
>
>   /* Flags used by pin/bind&friends. */
>   #define PIN_MAPPABLE	(1<<0)
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index f68f346..4bc0ce7 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -5356,3 +5356,50 @@ fail:
>   	drm_gem_object_unreference(&obj->base);
>   	return ERR_PTR(ret);
>   }
> +
> +/**
> + * i915_gem_object_vmap - map a GEM obj into kernel virtual space
> + * @obj: the GEM obj to be mapped
> + * @first: index of the first page where mapping starts
> + * @npages: how many pages to be mapped, starting from first page
> + *
> + * Map a given page range of GEM obj into kernel virtual space. The caller must
> + * make sure the associated pages are gathered and pinned before calling this
> + * function. vunmap should be called after use.
> + *
> + * NULL will be returned if fails.
> + */
> +void *i915_gem_object_vmap(struct drm_i915_gem_object *obj,
> +			   unsigned int first,
> +			   unsigned int npages)
> +{
> +	struct sg_page_iter sg_iter;
> +	struct page **pages;
> +	void *addr;
> +	int i;
> +
> +	if (first + npages > obj->pages->nents) {
> +		DRM_DEBUG_DRIVER("Invalid page count\n");
> +		return NULL;
> +	}
> +
> +	pages = drm_malloc_ab(npages, sizeof(*pages));
> +	if (pages == NULL) {
> +		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
> +		return NULL;
> +	}
> +
> +	i = 0;
> +	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first) {
> +		pages[i++] = sg_page_iter_page(&sg_iter);
> +		if (i == npages)
> +			break;
> +	}
> +
> +	addr = vmap(pages, npages, 0, PAGE_KERNEL);
> +	if (addr == NULL)
> +		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
> +	drm_free_large(pages);
> +
> +	return addr;
> +}
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index 1f3eef6..6133036 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -110,9 +110,7 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
>   {
>   	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
>   	struct drm_device *dev = obj->base.dev;
> -	struct sg_page_iter sg_iter;
> -	struct page **pages;
> -	int ret, i;
> +	int ret;
>
>   	ret = i915_mutex_lock_interruptible(dev);
>   	if (ret)
> @@ -131,16 +129,8 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
>
>   	ret = -ENOMEM;
>
> -	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
> -	if (pages == NULL)
> -		goto err_unpin;
> -
> -	i = 0;
> -	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
> -		pages[i++] = sg_page_iter_page(&sg_iter);
> -
> -	obj->dma_buf_vmapping = vmap(pages, i, 0, PAGE_KERNEL);
> -	drm_free_large(pages);
> +	obj->dma_buf_vmapping = i915_gem_object_vmap(obj, 0,
> +			dma_buf->size >> PAGE_SHIFT);
>
>   	if (!obj->dma_buf_vmapping)
>   		goto err_unpin;
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 45ce45a..93666e9 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -2064,27 +2064,6 @@ void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
>   	i915_gem_object_ggtt_unpin(ringbuf->obj);
>   }
>
> -static u32 *vmap_obj(struct drm_i915_gem_object *obj)
> -{
> -	struct sg_page_iter sg_iter;
> -	struct page **pages;
> -	void *addr;
> -	int i;
> -
> -	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
> -	if (pages == NULL)
> -		return NULL;
> -
> -	i = 0;
> -	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
> -		pages[i++] = sg_page_iter_page(&sg_iter);
> -
> -	addr = vmap(pages, i, 0, PAGE_KERNEL);
> -	drm_free_large(pages);
> -
> -	return addr;
> -}
> -
>   int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>   				     struct intel_ringbuffer *ringbuf)
>   {
> @@ -2103,7 +2082,8 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>   			return ret;
>   		}
>
> -		ringbuf->virtual_start = vmap_obj(obj);
> +		ringbuf->virtual_start = i915_gem_object_vmap(obj, 0,
> +				ringbuf->size >> PAGE_SHIFT);
>   		if (ringbuf->virtual_start == NULL) {
>   			i915_gem_object_ggtt_unpin(obj);
>   			return -ENOMEM;
>
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