[PATCH AUTOSEL 6.12 210/486] iommufd: Disallow allocating nested parent domain with fault ID

[Sasha Levin <sashal@kernel.org>]

From: Yi Liu <yi.l.liu@intel.com>

[ Upstream commit 1062d81086156e42878d701b816d2f368b53a77c ]

Allocating a domain with a fault ID indicates that the domain is faultable.
However, there is a gap for the nested parent domain to support PRI. Some
hardware lacks the capability to distinguish whether PRI occurs at stage 1
or stage 2. This limitation may require software-based page table walking
to resolve. Since no in-tree IOMMU driver currently supports this
functionality, it is disallowed. For more details, refer to the related
discussion at [1].

[1] https://lore.kernel.org/linux-iommu/bd1655c6-8b2f-4cfa-adb1-badc00d01811@intel.com/

Link: https://patch.msgid.link/r/20250226104012.82079-1-yi.l.liu@intel.com
Suggested-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/iommufd/hw_pagetable.c    | 3 +++
 tools/testing/selftests/iommu/iommufd.c | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index d06bf6e6c19fd..2454627a8b61b 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -122,6 +122,9 @@ iommufd_hwpt_paging_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
 	if ((flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING) &&
 	    !device_iommu_capable(idev->dev, IOMMU_CAP_DIRTY_TRACKING))
 		return ERR_PTR(-EOPNOTSUPP);
+	if ((flags & IOMMU_HWPT_FAULT_ID_VALID) &&
+	    (flags & IOMMU_HWPT_ALLOC_NEST_PARENT))
+		return ERR_PTR(-EOPNOTSUPP);
 
 	hwpt_paging = __iommufd_object_alloc(
 		ictx, hwpt_paging, IOMMUFD_OBJ_HWPT_PAGING, common.obj);
diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c
index 4927b9add5add..06f252733660a 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -289,6 +289,10 @@ TEST_F(iommufd_ioas, alloc_hwpt_nested)
 				    &test_hwpt_id);
 		test_err_hwpt_alloc(EINVAL, self->device_id, self->device_id, 0,
 				    &test_hwpt_id);
+		test_err_hwpt_alloc(EOPNOTSUPP, self->device_id, self->ioas_id,
+				    IOMMU_HWPT_ALLOC_NEST_PARENT |
+						IOMMU_HWPT_FAULT_ID_VALID,
+				    &test_hwpt_id);
 
 		test_cmd_hwpt_alloc(self->device_id, self->ioas_id,
 				    IOMMU_HWPT_ALLOC_NEST_PARENT,
-- 
2.39.5