Re: [PATCH] iommu: Unify iova_to_phys for identity domains

[Robin Murphy]

On 2021-07-15 02:38, Lu Baolu wrote:
On 7/15/21 1:28 AM, Robin Murphy wrote:
If people are going to insist on calling iommu_iova_to_phys()
pointlessly and expecting it to work, we can at least do ourselves a
favour by handling those cases in the core code, rather than repeatedly
across an inconsistent handful of drivers.
Signed-off-by: Robin Murphy <robin.mur...@arm.com>
---
  drivers/iommu/amd/io_pgtable.c              | 3 ---
  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 ---
  drivers/iommu/arm/arm-smmu/arm-smmu.c       | 3 ---
  drivers/iommu/iommu.c                       | 6 +++++-
  4 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/amd/io_pgtable.c 
b/drivers/iommu/amd/io_pgtable.c
index bb0ee5c9fde7..182c93a43efd 100644
--- a/drivers/iommu/amd/io_pgtable.c
+++ b/drivers/iommu/amd/io_pgtable.c
@@ -493,9 +493,6 @@ static phys_addr_t iommu_v1_iova_to_phys(struct 
io_pgtable_ops *ops, unsigned lo
      unsigned long offset_mask, pte_pgsize;
      u64 *pte, __pte;
-    if (pgtable->mode == PAGE_MODE_NONE)
-        return iova;
-
      pte = fetch_pte(pgtable, iova, &pte_pgsize);
      if (!pte || !IOMMU_PTE_PRESENT(*pte))
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c 
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 3e87a9cf6da3..c9fdd0d097be 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2481,9 +2481,6 @@ arm_smmu_iova_to_phys(struct iommu_domain 
*domain, dma_addr_t iova)
  {
      struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
-    if (domain->type == IOMMU_DOMAIN_IDENTITY)
-        return iova;
-
      if (!ops)
          return 0;
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c 
b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 0f181f76c31b..0d04eafa3fdb 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1317,9 +1317,6 @@ static phys_addr_t arm_smmu_iova_to_phys(struct 
iommu_domain *domain,
      struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
      struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
-    if (domain->type == IOMMU_DOMAIN_IDENTITY)
-        return iova;
-
      if (!ops)
          return 0;
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 43a2041d9629..7c16f977b5a6 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2371,7 +2371,11 @@ EXPORT_SYMBOL_GPL(iommu_detach_group);
  phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, 
dma_addr_t iova)
  {
-    if (unlikely(domain->ops->iova_to_phys == NULL))
+    if (domain->type == IOMMU_DOMAIN_IDENTITY)
+        return iova;
+
+    if (unlikely(domain->ops->iova_to_phys == NULL) ||
+        domain->type == IOMMU_DOMAIN_BLOCKED)
          return 0;

Nit:
Logically we only needs ops->iova_to_phys for DMA and UNMANAGED domains,
so it looks better if we have

     if (domain->type == IOMMU_DOMAIN_BLOCKED ||
         unlikely(domain->ops->iova_to_phys == NULL))
         return 0;

Yeah, I put IOMMU_DOMAIN_BLOCKED last as the least likely condition 
since it's really just for completeness - I don't think it's possible to 
see it legitimately used at the moment - but on second look I think 
ops->iova_to_phys == NULL is equally theoretical now, so maybe I could 
be removing that and we just make it mandatory for any new drivers?

Anyway,

Reviewed-by: Lu Baolu <baolu...@linux.intel.com>

Thanks!

Robin.


Best regards,
baolu

      return domain->ops->iova_to_phys(domain, iova);

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