[PATCH] iommufd/selftest: Add missing driver_ops for AMDV1 mock domain

[Pranjal Shrivastava <praan@google.com>]

syzbot found that allocating a mock domain with AMDV1 format could
cause a WARN_ON because the selftest enabled DYNAMIC_TOP without
providing the required driver_ops.

Initialize a spinlock (top_lock) and dummy callbacks in the mock
driver to satisfy the generic PT requirements.

Fixes: dcd6a011a8d5 ("iommupt: Add map_pages op")
Reported-by: syzbot+453eb7add07c3767adab@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69c1d50b.a70a0220.3cae05.0001.GAE@google.com/
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/iommufd/selftest.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index 9607416f8069..960c5aee4a09 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -119,6 +119,7 @@ struct mock_iommu_domain {
 		struct pt_iommu_amdv1 amdv1;
 	};
 	unsigned long flags;
+	spinlock_t top_lock;
 };
 PT_IOMMU_CHECK_DOMAIN(struct mock_iommu_domain, iommu, domain);
 PT_IOMMU_CHECK_DOMAIN(struct mock_iommu_domain, amdv1.iommu, domain);
@@ -129,6 +130,26 @@ to_mock_domain(struct iommu_domain *domain)
 	return container_of(domain, struct mock_iommu_domain, domain);
 }
 
+static void mock_domain_change_top(struct pt_iommu *iommu_table,
+				   phys_addr_t top_paddr,
+				   unsigned int top_level)
+{
+	/* The selftest doesn't have real hardware */
+}
+
+static spinlock_t *mock_domain_get_top_lock(struct pt_iommu *iommu_table)
+{
+	struct mock_iommu_domain *mock =
+		container_of(iommu_table, struct mock_iommu_domain, iommu);
+
+	return &mock->top_lock;
+}
+
+static const struct pt_iommu_driver_ops mock_driver_ops = {
+	.change_top = &mock_domain_change_top,
+	.get_top_lock = &mock_domain_get_top_lock,
+};
+
 struct mock_iommu_domain_nested {
 	struct iommu_domain domain;
 	struct mock_viommu *mock_viommu;
@@ -445,6 +466,8 @@ mock_domain_alloc_pgtable(struct device *dev,
 	if (!mock)
 		return ERR_PTR(-ENOMEM);
 	mock->domain.type = IOMMU_DOMAIN_UNMANAGED;
+	spin_lock_init(&mock->top_lock);
+	mock->amdv1.iommu.driver_ops = &mock_driver_ops;
 
 	mock->amdv1.iommu.nid = NUMA_NO_NODE;
 
-- 
2.53.0.1018.g2bb0e51243-goog