Commit 26b15eb0 authored by Matthew Auld's avatar Matthew Auld
Browse files

drm/i915/ttm: implement access_memory 

It looks like we need this for local-memory, if we want to use ptrace.
Something more is still needed if we want to handle non-mappable memory,
which looks quite annoying.

v2:
  - ttm_bo_kmap doesn't seem to work well here, and seems to expect
    contiguous resource.
v3(Andi):
  - s/PAGE_SIZE/bytes/ when passing in the size of the mapping.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/6989


Signed-off-by: default avatarMatthew Auld <matthew.auld@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221003172819.99245-1-matthew.auld@intel.com
parent c24538f5

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

+45 −0
Original line number Diff line number Diff line
@@ -699,6 +699,50 @@ static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo, 
	return ((base + sg_dma_address(sg)) >> PAGE_SHIFT) + ofs;

}



static int i915_ttm_access_memory(struct ttm_buffer_object *bo,

				  unsigned long offset, void *buf,

				  int len, int write)

{

	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

	resource_size_t iomap = obj->mm.region->iomap.base -

		obj->mm.region->region.start;

	unsigned long page = offset >> PAGE_SHIFT;

	unsigned long bytes_left = len;



	/*

	 * TODO: For now just let it fail if the resource is non-mappable,

	 * otherwise we need to perform the memcpy from the gpu here, without

	 * interfering with the object (like moving the entire thing).

	 */

	if (!i915_ttm_resource_mappable(bo->resource))

		return -EIO;



	offset -= page << PAGE_SHIFT;

	do {

		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);

		void __iomem *ptr;

		dma_addr_t daddr;



		daddr = i915_gem_object_get_dma_address(obj, page);

		ptr = ioremap_wc(iomap + daddr + offset, bytes);

		if (!ptr)

			return -EIO;



		if (write)

			memcpy_toio(ptr, buf, bytes);

		else

			memcpy_fromio(buf, ptr, bytes);

		iounmap(ptr);



		page++;

		buf += bytes;

		bytes_left -= bytes;

		offset = 0;

	} while (bytes_left);



	return len;

}



/*

 * All callbacks need to take care not to downcast a struct ttm_buffer_object

 * without checking its subclass, since it might be a TTM ghost object.
@@ -715,6 +759,7 @@ static struct ttm_device_funcs i915_ttm_bo_driver = { 
	.delete_mem_notify = i915_ttm_delete_mem_notify,

	.io_mem_reserve = i915_ttm_io_mem_reserve,

	.io_mem_pfn = i915_ttm_io_mem_pfn,

	.access_memory = i915_ttm_access_memory,

};



/**