iommu: Do not return 0 from map_pages if it doesn't do anything

These three implementations of map_pages() all succeed if a mapping is
requested with no read or write. Since they return back to __iommu_map()
leaving the mapped output as 0 it triggers an infinite loop. Therefore
nothing is using no-access protection bits.

Further, VFIO and iommufd rely on iommu_iova_to_phys() to get back PFNs
stored by map, if iommu_map() succeeds but iommu_iova_to_phys() fails that
will create serious bugs.

Thus remove this never used "nothing to do" concept and just fail map
immediately.

Fixes: e5fc975 ("iommu/io-pgtable: Add ARMv7 short descriptor support")
Fixes: e1d3c0f ("iommu: add ARM LPAE page table allocator")
Fixes: 745ef10 ("iommu/io-pgtable: Move Apple DART support to its own file")
Signed-off-by: Jason Gunthorpe <[email protected]>
Acked-by: Will Deacon <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: jgunthorpe

drivers/iommu/io-pgtable-arm-v7s.c

@@ -552,9 +552,8 @@ static int arm_v7s_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
 		    paddr >= (1ULL << data->iop.cfg.oas)))
 		return -ERANGE;
 
-	/* If no access, then nothing to do */
 	if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
-		return 0;
+		return -EINVAL;
 
 	while (pgcount--) {
 		ret = __arm_v7s_map(data, iova, paddr, pgsize, prot, 1, data->pgd,

drivers/iommu/io-pgtable-arm.c

@@ -515,9 +515,8 @@ static int arm_lpae_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
 	if (WARN_ON(iaext || paddr >> cfg->oas))
 		return -ERANGE;
 
-	/* If no access, then nothing to do */
 	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
-		return 0;
+		return -EINVAL;
 
 	prot = arm_lpae_prot_to_pte(data, iommu_prot);
 	ret = __arm_lpae_map(data, iova, paddr, pgsize, pgcount, prot, lvl,

drivers/iommu/io-pgtable-dart.c

@@ -245,9 +245,8 @@ static int dart_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
 	if (WARN_ON(paddr >> cfg->oas))
 		return -ERANGE;
 
-	/* If no access, then nothing to do */
 	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
-		return 0;
+		return -EINVAL;
 
 	tbl = dart_get_table(data, iova);