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From:   Eric Auger <eric.auger@redhat.com>
To:     eric.auger.pro@gmail.com, eric.auger@redhat.com,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org,
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        shameerali.kolothum.thodi@huawei.com, alex.williamson@redhat.com,
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Subject: [PATCH v11 10/13] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement
Date:   Tue, 14 Apr 2020 17:06:04 +0200
Message-Id: <20200414150607.28488-11-eric.auger@redhat.com>
In-Reply-To: <20200414150607.28488-1-eric.auger@redhat.com>
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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-smmu-v3.c | 41 +++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 38854c3e4083..f157d1de614b 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2896,6 +2896,37 @@ static void arm_smmu_detach_dev(struct arm_smmu_ma=
ster *master)
 	arm_smmu_install_ste_for_dev(master);
 }
=20
+static bool arm_smmu_share_msi_domain(struct iommu_domain *domain,
+				      struct device *dev)
+{
+	struct arm_smmu_domain *smmu_domain =3D to_smmu_domain(domain);
+	struct irq_domain *irqd =3D dev_get_msi_domain(dev);
+	struct arm_smmu_master *master;
+	unsigned long flags;
+	bool share =3D 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 =3D dev_get_msi_domain(master->dev);
+
+		if (!d)
+			continue;
+		if (irqd !=3D d) {
+			dev_info(dev, "Nested mode forbids to attach devices "
+				 "using different physical MSI doorbells "
+				 "to the same iommu_domain");
+			goto unlock;
+		}
+	}
+	share =3D true;
+unlock:
+	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
+	return share;
+}
+
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct devic=
e *dev)
 {
 	int ret =3D 0;
@@ -2937,6 +2968,16 @@ static int arm_smmu_attach_dev(struct iommu_domain=
 *domain, struct device *dev)
 		ret =3D -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 =3D=3D ARM_SMMU_DOMAIN_NESTED &&
+		!arm_smmu_share_msi_domain(domain, dev)) {
+		ret =3D -EINVAL;
+		goto out_unlock;
+	}
=20
 	master->domain =3D smmu_domain;
=20
--=20
2.20.1