Re: [PATCH v6 2/8] drm/ttm: Add ttm_bo_access

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Oct 31, 2024 at 04:43:19PM -0700, Matthew Brost wrote:
> On Thu, Oct 31, 2024 at 11:10:42AM -0700, Matthew Brost wrote:
> > Non-contiguous VRAM cannot easily be mapped in TTM nor can non-visible
> > VRAM easily be accessed. Add ttm_bo_access, which is similar to
> > ttm_bo_vm_access, to access such memory.
> > 
> > v4:
> >  - Fix checkpatch warnings (CI)
> > v5:
> >  - Fix checkpatch warnings (CI)
> > v6:
> >  - Fix kernel doc (Auld)
> > 
> 
> Christian - Do you mind if I merge patch along with the rest of the
> series to drm-xe-next?

Ray, Christian,

ack on getting this patch to drm-xe-next?

> 
> Matt
> 
> > Reported-by: Christoph Manszewski <christoph.manszewski@intel.com>
> > Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > Tested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> > Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> > ---
> >  drivers/gpu/drm/ttm/ttm_bo_util.c | 86 +++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/ttm/ttm_bo_vm.c   | 65 +----------------------
> >  include/drm/ttm/ttm_bo.h          |  2 +
> >  3 files changed, 89 insertions(+), 64 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > index d939925efa81..77e760ea7193 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > @@ -919,3 +919,89 @@ s64 ttm_lru_walk_for_evict(struct ttm_lru_walk *walk, struct ttm_device *bdev,
> >  
> >  	return progress;
> >  }
> > +
> > +static int ttm_bo_access_kmap(struct ttm_buffer_object *bo,
> > +			      unsigned long offset,
> > +			      void *buf, int len, int write)
> > +{
> > +	unsigned long page = offset >> PAGE_SHIFT;
> > +	unsigned long bytes_left = len;
> > +	int ret;
> > +
> > +	/* Copy a page at a time, that way no extra virtual address
> > +	 * mapping is needed
> > +	 */
> > +	offset -= page << PAGE_SHIFT;
> > +	do {
> > +		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
> > +		struct ttm_bo_kmap_obj map;
> > +		void *ptr;
> > +		bool is_iomem;
> > +
> > +		ret = ttm_bo_kmap(bo, page, 1, &map);
> > +		if (ret)
> > +			return ret;
> > +
> > +		ptr = (void *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
> > +		WARN_ON_ONCE(is_iomem);
> > +		if (write)
> > +			memcpy(ptr, buf, bytes);
> > +		else
> > +			memcpy(buf, ptr, bytes);
> > +		ttm_bo_kunmap(&map);
> > +
> > +		page++;
> > +		buf += bytes;
> > +		bytes_left -= bytes;
> > +		offset = 0;
> > +	} while (bytes_left);
> > +
> > +	return len;
> > +}
> > +
> > +/**
> > + * ttm_bo_access - Helper to access a buffer object
> > + *
> > + * @bo: ttm buffer object
> > + * @offset: access offset into buffer object
> > + * @buf: pointer to caller memory to read into or write from
> > + * @len: length of access
> > + * @write: write access
> > + *
> > + * Utility function to access a buffer object. Useful when buffer object cannot
> > + * be easily mapped (non-contiguous, non-visible, etc...).
> > + *
> > + * Returns:
> > + * @len if successful, negative error code on failure.
> > + */
> > +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> > +		  void *buf, int len, int write)
> > +{
> > +	int ret;
> > +
> > +	if (len < 1 || (offset + len) > bo->base.size)
> > +		return -EIO;
> > +
> > +	ret = ttm_bo_reserve(bo, true, false, NULL);
> > +	if (ret)
> > +		return ret;
> > +
> > +	switch (bo->resource->mem_type) {
> > +	case TTM_PL_SYSTEM:
> > +		fallthrough;
> > +	case TTM_PL_TT:
> > +		ret = ttm_bo_access_kmap(bo, offset, buf, len, write);
> > +		break;
> > +	default:
> > +		if (bo->bdev->funcs->access_memory)
> > +			ret = bo->bdev->funcs->access_memory
> > +				(bo, offset, buf, len, write);
> > +		else
> > +			ret = -EIO;
> > +	}
> > +
> > +	ttm_bo_unreserve(bo);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(ttm_bo_access);
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > index 2c699ed1963a..20b1e5f78684 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > @@ -366,45 +366,6 @@ void ttm_bo_vm_close(struct vm_area_struct *vma)
> >  }
> >  EXPORT_SYMBOL(ttm_bo_vm_close);
> >  
> > -static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
> > -				 unsigned long offset,
> > -				 uint8_t *buf, int len, int write)
> > -{
> > -	unsigned long page = offset >> PAGE_SHIFT;
> > -	unsigned long bytes_left = len;
> > -	int ret;
> > -
> > -	/* Copy a page at a time, that way no extra virtual address
> > -	 * mapping is needed
> > -	 */
> > -	offset -= page << PAGE_SHIFT;
> > -	do {
> > -		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
> > -		struct ttm_bo_kmap_obj map;
> > -		void *ptr;
> > -		bool is_iomem;
> > -
> > -		ret = ttm_bo_kmap(bo, page, 1, &map);
> > -		if (ret)
> > -			return ret;
> > -
> > -		ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
> > -		WARN_ON_ONCE(is_iomem);
> > -		if (write)
> > -			memcpy(ptr, buf, bytes);
> > -		else
> > -			memcpy(buf, ptr, bytes);
> > -		ttm_bo_kunmap(&map);
> > -
> > -		page++;
> > -		buf += bytes;
> > -		bytes_left -= bytes;
> > -		offset = 0;
> > -	} while (bytes_left);
> > -
> > -	return len;
> > -}
> > -
> >  int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> >  		     void *buf, int len, int write)
> >  {
> > @@ -412,32 +373,8 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> >  	unsigned long offset = (addr) - vma->vm_start +
> >  		((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
> >  		 << PAGE_SHIFT);
> > -	int ret;
> > -
> > -	if (len < 1 || (offset + len) > bo->base.size)
> > -		return -EIO;
> >  
> > -	ret = ttm_bo_reserve(bo, true, false, NULL);
> > -	if (ret)
> > -		return ret;
> > -
> > -	switch (bo->resource->mem_type) {
> > -	case TTM_PL_SYSTEM:
> > -		fallthrough;
> > -	case TTM_PL_TT:
> > -		ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);
> > -		break;
> > -	default:
> > -		if (bo->bdev->funcs->access_memory)
> > -			ret = bo->bdev->funcs->access_memory(
> > -				bo, offset, buf, len, write);
> > -		else
> > -			ret = -EIO;
> > -	}
> > -
> > -	ttm_bo_unreserve(bo);
> > -
> > -	return ret;
> > +	return ttm_bo_access(bo, offset, buf, len, write);
> >  }
> >  EXPORT_SYMBOL(ttm_bo_vm_access);
> >  
> > diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
> > index 5804408815be..8ea11cd8df39 100644
> > --- a/include/drm/ttm/ttm_bo.h
> > +++ b/include/drm/ttm/ttm_bo.h
> > @@ -421,6 +421,8 @@ void ttm_bo_unpin(struct ttm_buffer_object *bo);
> >  int ttm_bo_evict_first(struct ttm_device *bdev,
> >  		       struct ttm_resource_manager *man,
> >  		       struct ttm_operation_ctx *ctx);
> > +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> > +		  void *buf, int len, int write);
> >  vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
> >  			     struct vm_fault *vmf);
> >  vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> > -- 
> > 2.34.1
> >