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Subject: [PATCH 2/2] iommu: Fix the domain type checks when default_domain is
 set
From: Shivaprasad G Bhat <sbhat@linux.ibm.com>
To: iommu@lists.linux.dev, linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org, mpe@ellerman.id.au, npiggin@gmail.com,
        christophe.leroy@csgroup.eu, aneesh.kumar@kernel.org,
        naveen.n.rao@linux.ibm.com, jgg@ziepe.ca, jroedel@suse.de,
        tpearson@raptorengineering.com, aik@amd.com, bgray@linux.ibm.com,
        gregkh@linuxfoundation.org, sbhat@linux.ibm.com,
        gbatra@linux.vnet.ibm.com, vaibhav@linux.ibm.com
Date: Thu, 25 Jan 2024 06:08:52 -0600
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On PPC64, the iommu_ops.def_domain_type() is not defined and
CONFIG_IOMMU_DMA not enabled. With commit 0f6a90436a57 ("iommu: Do not
use IOMMU_DOMAIN_DMA if CONFIG_IOMMU_DMA is not enabled"), the
iommu_get_default_domain_type() return IOMMU_DOMAIN_IDENTITY. With
commit 2ad56efa80db ("powerpc/iommu: Setup a default domain and remove
set_platform_dma_ops"), the defaule_domain is set wih the type being
PLATFORM. With these two changes, iommu_group_alloc_default_domain()
ends up returning the NULL(with recent changes, ERR_PTR(-EINVAL))
leading to iommu_probe_device() failure and the device has no
iommu_group set in effect. Subsequently, the bind to vfio(VFIO_IOMMU)
fail as the iommu_group is not set for the device.

Make the iommu_get_default_domain_type() to take default_domain->type
into consideration along with default_domain_type() and fix
iommu_group_alloc_default_domain() to not error out if the requested
type is same as default domain type.

Fixes: 2ad56efa80db ("powerpc/iommu: Setup a default domain and remove set_platform_dma_ops")
Fixes: 0f6a90436a57 ("iommu: Do not use IOMMU_DOMAIN_DMA if CONFIG_IOMMU_DMA is not enabled")
Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
---
 drivers/iommu/iommu.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 68e648b55767..04083a1d9f7e 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -135,6 +135,8 @@ static struct group_device *iommu_group_alloc_device(struct iommu_group *group,
 						     struct device *dev);
 static void __iommu_group_free_device(struct iommu_group *group,
 				      struct group_device *grp_dev);
+static int iommu_get_def_domain_type(struct iommu_group *group,
+				     struct device *dev, int cur_type);
 
 #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store)		\
 struct iommu_group_attribute iommu_group_attr_##_name =		\
@@ -1788,7 +1790,8 @@ __iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 static struct iommu_domain *
 iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 {
-	const struct iommu_ops *ops = dev_iommu_ops(iommu_group_first_dev(group));
+	struct device *dev = iommu_group_first_dev(group);
+	const struct iommu_ops *ops = dev_iommu_ops(dev);
 	struct iommu_domain *dom;
 
 	lockdep_assert_held(&group->mutex);
@@ -1799,7 +1802,7 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 	 * domain. Do not use in new drivers.
 	 */
 	if (ops->default_domain) {
-		if (req_type)
+		if (iommu_get_def_domain_type(group, dev, req_type) != req_type)
 			return ERR_PTR(-EINVAL);
 		return ops->default_domain;
 	}
@@ -1871,10 +1874,13 @@ static int iommu_get_def_domain_type(struct iommu_group *group,
 	const struct iommu_ops *ops = dev_iommu_ops(dev);
 	int type;
 
-	if (!ops->def_domain_type)
+	if (ops->def_domain_type)
+		type = ops->def_domain_type(dev);
+	else if (group->default_domain)
+		type = group->default_domain->type;
+	else
 		return cur_type;
 
-	type = ops->def_domain_type(dev);
 	if (!type || cur_type == type)
 		return cur_type;
 	if (!cur_type)