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

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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: 8e7460eac7 ("drm/panthor: Support partial unmaps of huge pages")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20260408191228.537625-1-adrian.larumbe@collabora.com
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
This commit is contained in:
Adrián Larumbe 2026-04-08 20:12:23 +01:00
parent 2d76319c4c
commit 8867262d99
1 changed files with 19 additions and 0 deletions
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19
drivers/gpu/drm/panthor/panthor_mmu.c
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@ -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 */