[PATCH v8 19/29] iommu/smmuv3: Enforce incompatibility between nested mode and HW MSI regions

[Eric Auger]

Nested mode currently is not compatible with HW MSI reserved regions.
Indeed MSI transactions targeting this MSI doorbells bypass the SMMU.

Let's check nested mode is not attempted in such configuration.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
---
 drivers/iommu/arm-smmu-v3.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 31d8028bb997..2621c3b7cf73 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2079,6 +2079,23 @@ static bool arm_smmu_share_msi_domain(struct iommu_domain *domain,
 	return share;
 }
 
+static bool arm_smmu_has_hw_msi_resv_region(struct device *dev)
+{
+	struct iommu_resv_region *region;
+	bool has_msi_resv_region = false;
+	LIST_HEAD(resv_regions);
+
+	iommu_get_resv_regions(dev, &resv_regions);
+	list_for_each_entry(region, &resv_regions, list) {
+		if (region->type == IOMMU_RESV_MSI) {
+			has_msi_resv_region = true;
+			break;
+		}
+	}
+	iommu_put_resv_regions(dev, &resv_regions);
+	return has_msi_resv_region;
+}
+
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
 	int ret = 0;
@@ -2116,10 +2133,12 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	/*
 	 * In nested mode we must check all devices belonging to the
 	 * domain share the same physical MSI doorbell. Otherwise nested
-	 * stage MSI binding is not supported.
+	 * stage MSI binding is not supported. Also nested mode is not
+	 * compatible with MSI HW reserved regions.
 	 */
 	if (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED &&
-		!arm_smmu_share_msi_domain(domain, dev)) {
+		(!arm_smmu_share_msi_domain(domain, dev) ||
+		 arm_smmu_has_hw_msi_resv_region(dev))) {
 		ret = -EINVAL;
 		goto out_unlock;
 	}
-- 
2.20.1