[PATCH] armv8: mmu: don't panic when unmapping a page which isn't mapped

[Casey Connolly]

If a caller tries to unmap a single page which is already part of an
unmapped block, set_one_region() will panic since there isn't a valid
block or table to contain the page. Detect this case explicitly and
return since no action needs to be taken.

Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
---
Depends on my previous series which fixes unmapping regions

https://lore.kernel.org/u-boot/20260608-b4-mmu-unmap-fixes-v6-0-ac0764cccf40@linaro.org/
---
 arch/arm/cpu/armv8/cache_v8.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
index 6c85022556ad..472887b5d99b 100644
--- a/arch/arm/cpu/armv8/cache_v8.c
+++ b/arch/arm/cpu/armv8/cache_v8.c
@@ -1003,8 +1003,13 @@ static u64 set_one_region(u64 start, u64 size, u64 attrs, bool flag, int level)
 	int levelshift = level2shift(level);
 	u64 levelsize = 1ULL << levelshift;
 	u64 *pte = find_pte(start, level);
 
+	/* Trying to unmap a region which is part of an already unmapped block, nothing to do */
+	if (pte_type(pte) == PTE_TYPE_FAULT && attrs == PTE_TYPE_FAULT && size < levelsize) {
+		return size;
+	}
+
 	/* Can we can just modify the current level block/page? */
 	if (is_aligned(start, size, levelsize)) {
 		if (attrs == PTE_TYPE_FAULT) {
 			if (pte_type(pte) == PTE_TYPE_TABLE && level < 3)
-- 
2.53.0