Re: [PATCH i-g-t 1/2] lib/xe: Introduce aligned buffer mapping

["Hellstrom, Thomas" <thomas.hellstrom@intel.com>]

On Wed, 2026-03-11 at 17:03 +0000, nishit.sharma@intel.com wrote:
> From: Nishit Sharma <nishit.sharma@intel.com>
> 
> Added aligned buffer mapping which is providing an interface for
> mapping
> buffer objects with a specified alignment. This API improves
> cross-platform compatibility and simplifies batch buffer setup by
> eliminating the need for platform-specific address handling.
> 
> Signed-off-by: Thomas Hellstrom <thomas.hellstrom@intel.com>
> Signed-off-by: Nishit Sharma <nishit.sharma@intel.com>
> ---
>  lib/xe/xe_ioctl.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  lib/xe/xe_ioctl.h |  1 +
>  2 files changed, 41 insertions(+)
> 
> diff --git a/lib/xe/xe_ioctl.c b/lib/xe/xe_ioctl.c
> index 16aae05c9..2e9e75656 100644
> --- a/lib/xe/xe_ioctl.c
> +++ b/lib/xe/xe_ioctl.c
> @@ -579,6 +579,46 @@ void *xe_bo_map_fixed(int fd, uint32_t bo,
> size_t size, uint64_t addr)
>  	return map;
>  }
>  
> +/**
> + * xe_bo_map_aligned() - Create a bo CPU map requiring an alignment
> for the
> + * returned address.
> + * @fd: The device file-descriptor
> + * @bo: The buffer object
> + * @size: The size of the map
> + * @alignment: The requested map alingment.

s/alingment/alignment/

Return:

> + */
> +void *xe_bo_map_aligned(int fd, uint32_t bo, size_t size, size_t
> alignment)
> +{
> +	size_t anon_size = size + alignment;
> +	uint64_t anon_addr;
> +	void *anon_map, *map;
> +	uint64_t map_addr;
> +	size_t hole_size;
> +
> +
> +	/* Reserve a range of virtual space where we can fit an
> aligned map */
> +	anon_map = mmap(NULL, anon_size, PROT_NONE, MAP_PRIVATE |
> MAP_ANONYMOUS, -1, 0);
> +	igt_assert(anon_map != MAP_FAILED);
> +	anon_addr = to_user_pointer(anon_map);
> +
> +	/* Compute the first aligned address within the virtual
> space. */
> +	map_addr = ALIGN(anon_addr, alignment);
> +	/* Map the bo there, replacing part of the reserved virtual
> range. */
> +	map = xe_bo_map_fixed(fd, bo, size, map_addr);

Perhaps an igt_assert() that map is indeed properly aligned.

> +
> +	/* Unreserve part of the virtual range (if any) *before* the
> bo map */
> +	hole_size = map_addr - anon_addr;
> +	if (hole_size)
> +		igt_assert(munmap(anon_map, hole_size) == 0);
> +
> +	/* Unreserve part of the virtual range (if any) *after* the
> bo map */
> +	hole_size = anon_size - hole_size - size;
> +	if (hole_size)
> +		igt_assert(munmap(map + size, hole_size) == 0);
> +
> +	return map;
> +}
> +
>  void *xe_bo_mmap_ext(int fd, uint32_t bo, size_t size, int prot)
>  {
>  	return __xe_bo_map(fd, bo, size, prot);
> diff --git a/lib/xe/xe_ioctl.h b/lib/xe/xe_ioctl.h
> index 3ea651063..b62d259fd 100644
> --- a/lib/xe/xe_ioctl.h
> +++ b/lib/xe/xe_ioctl.h
> @@ -91,6 +91,7 @@ void xe_exec_queue_destroy(int fd, uint32_t
> exec_queue);
>  uint64_t xe_bo_mmap_offset(int fd, uint32_t bo);
>  void *xe_bo_map(int fd, uint32_t bo, size_t size);
>  void *xe_bo_map_fixed(int fd, uint32_t bo, size_t size, uint64_t
> addr);
> +void *xe_bo_map_aligned(int fd, uint32_t bo, size_t size, size_t
> alignment);
>  void *xe_bo_mmap_ext(int fd, uint32_t bo, size_t size, int prot);
>  int __xe_exec(int fd, struct drm_xe_exec *exec);
>  void xe_exec(int fd, struct drm_xe_exec *exec);

Otherwise need an additional reviewer, since I contributed to the
patch.

Thanks,
Thomas