iommu/arm-smmu-v3: Link domains and devices

When removing a mapping from a domain, we need to send an invalidation to
all devices that might have stored it in their Address Translation Cache
(ATC). In addition when updating the context descriptor of a live domain,
we'll need to send invalidations for all devices attached to it.

Maintain a list of devices in each domain, protected by a spinlock. It is
updated every time we attach or detach devices to and from domains.

It needs to be a spinlock because we'll invalidate ATC entries from
within hardirq-safe contexts, but it may be possible to relax the read
side with RCU later.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu-v3.c

@@ -581,6 +581,7 @@ struct arm_smmu_device {
 struct arm_smmu_master {
 	struct arm_smmu_device		*smmu;
 	struct arm_smmu_domain		*domain;
+	struct list_head		domain_head;
 	u32				*sids;
 	unsigned int			num_sids;
 };
@@ -607,6 +608,9 @@ struct arm_smmu_domain {
 	};
 
 	struct iommu_domain		domain;
+
+	struct list_head		devices;
+	spinlock_t			devices_lock;
 };
 
 struct arm_smmu_option_prop {
@@ -1504,6 +1508,9 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
 	}
 
 	mutex_init(&smmu_domain->init_mutex);
+	INIT_LIST_HEAD(&smmu_domain->devices);
+	spin_lock_init(&smmu_domain->devices_lock);
+
 	return &smmu_domain->domain;
 }
 
@@ -1721,16 +1728,24 @@ static void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master)
 
 static void arm_smmu_detach_dev(struct arm_smmu_master *master)
 {
-	if (!master->domain)
+	unsigned long flags;
+	struct arm_smmu_domain *smmu_domain = master->domain;
+
+	if (!smmu_domain)
 		return;
 
+	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
+	list_del(&master->domain_head);
+	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
+
 	master->domain = NULL;
 	arm_smmu_install_ste_for_dev(master);
 }
 
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
 	int ret = 0;
+	unsigned long flags;
 	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
 	struct arm_smmu_device *smmu;
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
@@ -1764,6 +1779,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 	master->domain = smmu_domain;
 
+	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
+	list_add(&master->domain_head, &smmu_domain->devices);
+	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
+
 	if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1)
 		arm_smmu_write_ctx_desc(smmu, &smmu_domain->s1_cfg);