linux-kernel - [PATCH v12 10/15] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement

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Date:   Mon, 16 Nov 2020 11:43:11 +0100
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu, will@...nel.org,
        joro@...tes.org, maz@...nel.org, robin.murphy@....com
Cc:     jean-philippe@...aro.org, zhangfei.gao@...aro.org,
        zhangfei.gao@...il.com, vivek.gautam@....com,
        shameerali.kolothum.thodi@...wei.com, alex.williamson@...hat.com,
        jacob.jun.pan@...ux.intel.com, yi.l.liu@...el.com, tn@...ihalf.com,
        nicoleotsuka@...il.com
Subject: [PATCH v12 10/15] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement

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@...hat.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 4b796693d697..de03ac111f76 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2265,6 +2265,37 @@ 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;
@@ -2316,6 +2347,16 @@ 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;
 
-- 
2.21.3