[PATCH 6/6] iommu: Make set_dev_pasid op support domain replacement

[Yi Liu <yi.l.liu@intel.com>]

The iommu core is going to support domain replacement for pasid, it needs
to make the set_dev_pasid op support replacing domain and keep the old
domain config in the failure case.

Currently only the Intel iommu driver supports the latest set_dev_pasid
op definition. ARM and AMD iommu driver do not support domain replacement
for pasid yet, both drivers would fail the set_dev_pasid op to keep the
old config if the input @old is non-NULL.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/iommu/amd/pasid.c                       | 3 +++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 +++
 include/linux/iommu.h                           | 3 ++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/pasid.c b/drivers/iommu/amd/pasid.c
index 77bf5f5f947a..30e27bda3fac 100644
--- a/drivers/iommu/amd/pasid.c
+++ b/drivers/iommu/amd/pasid.c
@@ -109,6 +109,9 @@ int iommu_sva_set_dev_pasid(struct iommu_domain *domain,
 	unsigned long flags;
 	int ret = -EINVAL;
 
+	if (old)
+		return -EOPNOTSUPP;
+
 	/* PASID zero is used for requests from the I/O device without PASID */
 	if (!is_pasid_valid(dev_data, pasid))
 		return ret;
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index c058949749cb..a1e411c71efa 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -637,6 +637,9 @@ static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
 	int ret = 0;
 	struct mm_struct *mm = domain->mm;
 
+	if (old)
+		return -EOPNOTSUPP;
+
 	if (mm_get_enqcmd_pasid(mm) != id)
 		return -EINVAL;
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index a33f53aab61b..3259f77ff2e3 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -607,7 +607,8 @@ struct iommu_ops {
  * * EBUSY	- device is attached to a domain and cannot be changed
  * * ENODEV	- device specific errors, not able to be attached
  * * <others>	- treated as ENODEV by the caller. Use is discouraged
- * @set_dev_pasid: set an iommu domain to a pasid of device
+ * @set_dev_pasid: set or replace an iommu domain to a pasid of device. The pasid of
+ *                 the device should be left in the old config in error case.
  * @map_pages: map a physically contiguous set of pages of the same size to
  *             an iommu domain.
  * @unmap_pages: unmap a number of pages of the same size from an iommu domain
-- 
2.34.1