ANDROID: iommu/io-pgtable-arm: Don't return on invalid ptes

The walker can be called for a range that contains invalid PTEs,
For example, with a table that has some already unmapped pages,
It's valid to unmap the whole table at once or even overwrite it
with a block, that will trigger flush_walk() operation for the
full table range which is not all valid.
So, the flush_walk() will walk the whole range and decrement the
refcount of the valid ptes which can be scattered.

Bug: 357781595
Bug: 384432312
Change-Id: If32bd389f29bbe5f6fedf1537cafc3f2badecc63
Signed-off-by: Mostafa Saleh <smostafa@google.com>

drivers/iommu/io-pgtable-arm-common.c

@@ -551,7 +551,7 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
 	int ret;
 
 	ret = __arm_lpae_iopte_walk(data, &walk_data, data->pgd, data->start_level);
-	if (ret)
+	if (ret || !iopte_valid(d.pte))
 		return 0;
 
 	iova &= (ARM_LPAE_BLOCK_SIZE(d.lvl, data) - 1);
@@ -614,8 +614,11 @@ static int io_pgtable_visit(struct arm_lpae_io_pgtable *data,
 		return 0;
 	}
 
-	if (!is_table)
-		return -EINVAL;
+	/* Don't fail the walk if one entry is invalid, just skip over it */
+	if (!is_table) {
+		walk_data->addr += size;
+		return 0;
+	}
 
 	ptep = iopte_deref(pte, data);