[PATCH v14 09/13] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement

Eric Auger
2021-02-23T20:58:51Z

In nested mode we enforce the rule that all devices belonging
to the same iommu_domain share the same msi_domain.

Indeed if there were several physical MSI doorbells being used
within a single iommu_domain, it becomes really difficult to
resolve the nested stage mapping translating into the correct
physical doorbell. So let's forbid this situation.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 41 +++++++++++++++++++++
1 file changed, 41 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index df3adc49111c..0cf92cd0ab3e 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2429,6 +2429,37 @@ static void arm_smmu_detach_dev(struct arm_smmu_master *master)
arm_smmu_install_ste_for_dev(master);
}

+static bool arm_smmu_share_msi_domain(struct iommu_domain *domain,
+ struct device *dev)
+{
+ struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+ struct irq_domain *irqd = dev_get_msi_domain(dev);
+ struct arm_smmu_master *master;
+ unsigned long flags;
+ bool share = false;
+
+ if (!irqd)
+ return true;
+
+ spin_lock_irqsave(&smmu_domain->devices_lock, flags);
+ list_for_each_entry(master, &smmu_domain->devices, domain_head) {
+ struct irq_domain *d = dev_get_msi_domain(master->dev);
+
+ if (!d)
+ continue;
+ if (irqd != d) {
+ dev_info(dev, "Nested mode forbids to attach devices "
+ "using different physical MSI doorbells "
+ "to the same iommu_domain");
+ goto unlock;
+ }
+ }
+ share = true;
+unlock:
+ spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
+ return share;
+}
+
static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
{
int ret = 0;
@@ -2486,6 +2517,16 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
ret = -EINVAL;
goto out_unlock;
}
+ /*
+ * 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.
+ */
+ if (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED &&
+ !arm_smmu_share_msi_domain(domain, dev)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }

master->domain = smmu_domain;

--
2.26.2