Commit 8867262d authored by Adrián Larumbe's avatar Adrián Larumbe
Browse files

drm/panthor: Extend VM locked region for remap case to be a superset 



In the event of an sm_step_remap() that leads to a partial unmap of a
transparent huge page, the new locked region required by an extended unmap
might not be a superset of the original one. Then, if it leaves a portion
of the initially requested one out, the ensuing map will trigger a warning.

Fixes: 8e7460ea ("drm/panthor: Support partial unmaps of huge pages")
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20260408191228.537625-1-adrian.larumbe@collabora.com


Signed-off-by: default avatarAdrián Larumbe <adrian.larumbe@collabora.com>
parent 2d76319c

drivers/gpu/drm/panthor/panthor_mmu.c

+19 −0
Original line number Diff line number Diff line
@@ -1638,6 +1638,25 @@ static int panthor_vm_lock_region(struct panthor_vm *vm, u64 start, u64 size) 
	    start + size <= vm->locked_region.start + vm->locked_region.size)

		return 0;



	/* sm_step_remap() may need a locked region that isn't a strict superset

	 * of the original one because of having to extend unmap boundaries beyond

	 * it to deal with partial unmaps of transparent huge pages. What we want

	 * in those cases is to lock the union of both regions. The new region must

	 * always overlap with the original one, because the upper and lower unmap

	 * boundaries in a remap operation can only shift up or down respectively,

	 * but never otherwise.

	 */

	if (vm->locked_region.size) {

		u64 end = max(vm->locked_region.start + vm->locked_region.size,

			      start + size);



		drm_WARN_ON_ONCE(&vm->ptdev->base, (start + size <= vm->locked_region.start) ||

				 (start >= vm->locked_region.start + vm->locked_region.size));



		start = min(start, vm->locked_region.start);

		size = end - start;

	}



	mutex_lock(&ptdev->mmu->as.slots_lock);

	if (vm->as.id >= 0 && size) {

		/* Lock the region that needs to be updated */