iommu: arm-smmu: fix check for need for preallocate memory

commit b312b4f0e2f9 ("iommu: arm-smmu: Preallocate memory for map
only on failure") had the following two errors:

  1. The return code we checking when map_sg fails and we preallocte
     is wrong. The check should be for 0 and not -ENOMEM.
     So the preallocate is never happening when map_sg fails.

  2. map_sg could've have mapped certain elements in sglist and later
     had got failed. With proper check, we are trying to call map_sg
     on the same size again, which would leave to double map of
     previously mapped elements in sglist.

Fix this by returning the actual ret code from arm_lpae_map_sg()
and check it against -ENOMEM if we need to preallocate or not.
Also, unmap any partial iovas that was mapped previously.

Change-Id: Ifee7c0bed6b9cf1c35ebb4a03d51a1a80ab0ed58
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
Signed-off-by: Ruchit <ruchitmarathe@gmail.com>

drivers/iommu/arm-smmu.c

@@ -3155,8 +3155,13 @@ static size_t arm_smmu_map_sg(struct iommu_domain *domain, unsigned long iova,
 				  prot, &size);
 		spin_unlock_irqrestore(&smmu_domain->cb_lock, flags);
 
-
 		if (ret == -ENOMEM) {
+			/* unmap any partially mapped iova */
+			if (size) {
+				arm_smmu_secure_domain_unlock(smmu_domain);
+				arm_smmu_unmap(domain, iova, size);
+				arm_smmu_secure_domain_lock(smmu_domain);
+			}
 			arm_smmu_prealloc_memory(smmu_domain,
 						 batch_size, &nonsecure_pool);
 			spin_lock_irqsave(&smmu_domain->cb_lock, flags);
@@ -3171,8 +3176,8 @@ static size_t arm_smmu_map_sg(struct iommu_domain *domain, unsigned long iova,
 							 &nonsecure_pool);
 		}
 
-		/* Returns 0 on error */
-		if (!ret) {
+		/* Returns -ve val on error */
+		if (ret < 0) {
 			size_to_unmap = iova + size - __saved_iova_start;
 			goto out;
 		}
@@ -3180,6 +3185,7 @@ static size_t arm_smmu_map_sg(struct iommu_domain *domain, unsigned long iova,
 		iova += batch_size;
 		idx_start = idx_end;
 		sg_start = sg_end;
+		size = 0;
 	}
 
 out:

drivers/iommu/io-pgtable-arm.c

@@ -634,7 +634,8 @@ static int arm_lpae_map_sg(struct io_pgtable_ops *ops, unsigned long iova,
 	arm_lpae_iopte prot;
 	struct scatterlist *s;
 	size_t mapped = 0;
-	int i, ret;
+	int i;
+	int ret = -EINVAL;
 	unsigned int min_pagesz;
 	struct io_pgtable_cfg *cfg = &data->iop.cfg;
 	struct map_state ms;
@@ -705,7 +706,7 @@ static int arm_lpae_map_sg(struct io_pgtable_ops *ops, unsigned long iova,
 out_err:
 	/* Return the size of the partial mapping so that they can be undone */
 	*size = mapped;
-	return 0;
+	return ret;
 }
 
 static void __arm_lpae_free_pgtable(struct arm_lpae_io_pgtable *data, int lvl,

drivers/iommu/io-pgtable.h

@@ -156,8 +156,8 @@ struct io_pgtable_cfg {
  *
  * @map:		Map a physically contiguous memory region.
  * @map_sg:		Map a scatterlist.  Returns the number of bytes mapped,
- *			or 0 on failure.  The size parameter contains the size
- *			of the partial mapping in case of failure.
+ *			or -ve val on failure.  The size parameter contains the
+ *			size of the partial mapping in case of failure.
  * @unmap:		Unmap a physically contiguous memory region.
  * @iova_to_phys:	Translate iova to physical address.
  * @is_iova_coherent:	Checks coherency of given IOVA. Returns True if coherent