Commit 255fc170 authored by Andi Shyti's avatar Andi Shyti
Browse files

drm/i915/gem: Calculate object page offset for partial memory mapping 



To enable partial memory mapping of GPU virtual memory, it's
necessary to introduce an offset to the object's memory
(obj->mm.pages) scatterlist. This adjustment compensates for
instances when userspace mappings do not start from the beginning
of the object.

Based on a patch by Chris Wilson.

Signed-off-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: default avatarNirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240807100521.478266-3-andi.shyti@linux.intel.com
parent 609d8b1c

drivers/gpu/drm/i915/gem/i915_gem_mman.c

+3 −1
Original line number Diff line number Diff line
@@ -252,6 +252,7 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf) 
	struct vm_area_struct *area = vmf->vma;

	struct i915_mmap_offset *mmo = area->vm_private_data;

	struct drm_i915_gem_object *obj = mmo->obj;

	unsigned long obj_offset;

	resource_size_t iomap;

	int err;
@@ -273,10 +274,11 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf) 
		iomap -= obj->mm.region->region.start;

	}



	obj_offset = area->vm_pgoff - drm_vma_node_start(&mmo->vma_node);

	/* PTEs are revoked in obj->ops->put_pages() */

	err = remap_io_sg(area,

			  area->vm_start, area->vm_end - area->vm_start,

			  obj->mm.pages->sgl, iomap);

			  obj->mm.pages->sgl, obj_offset, iomap);



	if (area->vm_flags & VM_WRITE) {

		GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));

drivers/gpu/drm/i915/i915_mm.c

+11 −1
Original line number Diff line number Diff line
@@ -122,13 +122,15 @@ int remap_io_mapping(struct vm_area_struct *vma, 
 * @addr: target user address to start at

 * @size: size of map area

 * @sgl: Start sg entry

 * @offset: offset from the start of the page

 * @iobase: Use stored dma address offset by this address or pfn if -1

 *

 *  Note: this is only safe if the mm semaphore is held when called.

 */

int remap_io_sg(struct vm_area_struct *vma,

		unsigned long addr, unsigned long size,

		struct scatterlist *sgl, resource_size_t iobase)

		struct scatterlist *sgl, unsigned long offset,

		resource_size_t iobase)

{

	struct remap_pfn r = {

		.mm = vma->vm_mm,
@@ -141,6 +143,14 @@ int remap_io_sg(struct vm_area_struct *vma, 
	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */

	GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);



	while (offset >= sg_dma_len(r.sgt.sgp) >> PAGE_SHIFT) {

		offset -= sg_dma_len(r.sgt.sgp) >> PAGE_SHIFT;

		r.sgt = __sgt_iter(__sg_next(r.sgt.sgp), use_dma(iobase));

		if (!r.sgt.sgp)

			return -EINVAL;

	}

	r.sgt.curr = offset << PAGE_SHIFT;



	if (!use_dma(iobase))

		flush_cache_range(vma, addr, size);

drivers/gpu/drm/i915/i915_mm.h

+2 −1
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ int remap_io_mapping(struct vm_area_struct *vma, 


int remap_io_sg(struct vm_area_struct *vma,

		unsigned long addr, unsigned long size,

		struct scatterlist *sgl, resource_size_t iobase);

		struct scatterlist *sgl, unsigned long offset,

		resource_size_t iobase);



#endif /* __I915_MM_H__ */