iommu/io-pgtable-arm: Rationalise size check

It makes little sense to only validate the requested size after we think
we've found a matching block size - making the check up-front is simple,
and far more logical than waiting to walk off the bottom of the table to
infer that we must have been passed a bogus size to start with.

We're missing an equivalent check on the unmap path, so add that as well
for consistency.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/io-pgtable-arm.c

@@ -392,7 +392,7 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
 	ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
 
 	/* If we can install a leaf entry at this level, then do so */
-	if (size == block_size && (size & cfg->pgsize_bitmap))
+	if (size == block_size)
 		return arm_lpae_init_pte(data, iova, paddr, prot, lvl, ptep);
 
 	/* We can't allocate tables at the final level */
@@ -479,6 +479,7 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
 			phys_addr_t paddr, size_t size, int iommu_prot)
 {
 	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	struct io_pgtable_cfg *cfg = &data->iop.cfg;
 	arm_lpae_iopte *ptep = data->pgd;
 	int ret, lvl = ARM_LPAE_START_LVL(data);
 	arm_lpae_iopte prot;
@@ -487,6 +488,9 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
 	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
 		return 0;
 
+	if (WARN_ON(!size || (size & cfg->pgsize_bitmap) != size))
+		return -EINVAL;
+
 	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
 		    paddr >= (1ULL << data->iop.cfg.oas)))
 		return -ERANGE;
@@ -652,9 +656,13 @@ static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova,
 			     size_t size, struct iommu_iotlb_gather *gather)
 {
 	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	struct io_pgtable_cfg *cfg = &data->iop.cfg;
 	arm_lpae_iopte *ptep = data->pgd;
 	int lvl = ARM_LPAE_START_LVL(data);
 
+	if (WARN_ON(!size || (size & cfg->pgsize_bitmap) != size))
+		return 0;
+
 	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias)))
 		return 0;