Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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: 8e7460eac786 ("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>
+19
+19
drivers/gpu/drm/panthor/panthor_mmu.c
+19
drivers/gpu/drm/panthor/panthor_mmu.c
···
1638
1638
start + size <= vm->locked_region.start + vm->locked_region.size)
1639
1639
return 0;
1640
1640
1641
+
/* sm_step_remap() may need a locked region that isn't a strict superset
1642
+
* of the original one because of having to extend unmap boundaries beyond
1643
+
* it to deal with partial unmaps of transparent huge pages. What we want
1644
+
* in those cases is to lock the union of both regions. The new region must
1645
+
* always overlap with the original one, because the upper and lower unmap
1646
+
* boundaries in a remap operation can only shift up or down respectively,
1647
+
* but never otherwise.
1648
+
*/
1649
+
if (vm->locked_region.size) {
1650
+
u64 end = max(vm->locked_region.start + vm->locked_region.size,
1651
+
start + size);
1652
+
1653
+
drm_WARN_ON_ONCE(&vm->ptdev->base, (start + size <= vm->locked_region.start) ||
1654
+
(start >= vm->locked_region.start + vm->locked_region.size));
1655
+
1656
+
start = min(start, vm->locked_region.start);
1657
+
size = end - start;
1658
+
}
1659
+
1641
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mutex_lock(&ptdev->mmu->as.slots_lock);
1642
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if (vm->as.id >= 0 && size) {
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/* Lock the region that needs to be updated */