iommu/arm-smmu: Don't fail device attach if already attached to a domain

The ARM SMMU attach_dev implementations returns -EEXIST if the device
being attached is already attached to a domain. This doesn't play nicely
with the default domain, resulting in splats such as:

  WARNING: at drivers/iommu/iommu.c:1257
  Modules linked in:

  CPU: 3 PID: 1939 Comm: virtio-net-tx Tainted: G S              4.5.0-rc4+ #1
  Hardware name: FVP Base (DT)
  task: ffffffc87a9d0000 ti: ffffffc07a278000 task.ti: ffffffc07a278000
  PC is at __iommu_detach_group+0x68/0xe8
  LR is at __iommu_detach_group+0x48/0xe8

This patch fixes the problem by forcefully detaching the device from
its old domain, if present, when attaching to a new one. The unused
->detach_dev callback is also removed the iommu_ops structures.

Signed-off-by: Will Deacon <will.deacon@arm.com>

2 files changed, 26 insertions, 40 deletions

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index f003b3ab646b..d96d45ddf500 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1638,6 +1638,17 @@ static int arm_smmu_install_ste_for_group(struct arm_smmu_group *smmu_group)
         return 0;
 }
 
+static void arm_smmu_detach_dev(struct device *dev)
+{
+        struct arm_smmu_group *smmu_group = arm_smmu_group_get(dev);
+
+        smmu_group->ste.bypass = true;
+        if (IS_ERR_VALUE(arm_smmu_install_ste_for_group(smmu_group)))
+                dev_warn(dev, "failed to install bypass STE\n");
+
+        smmu_group->domain = NULL;
+}
+
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
         int ret = 0;
@@ -1650,7 +1661,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
         /* Already attached to a different domain? */
         if (smmu_group->domain && smmu_group->domain != smmu_domain)
-                return -EEXIST;
+                arm_smmu_detach_dev(dev);
 
         smmu = smmu_group->smmu;
         mutex_lock(&smmu_domain->init_mutex);
@@ -1687,25 +1698,6 @@ out_unlock:
         return ret;
 }
 
-static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
-{
-        struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-        struct arm_smmu_group *smmu_group = arm_smmu_group_get(dev);
-
-        BUG_ON(!smmu_domain);
-        BUG_ON(!smmu_group);
-
-        mutex_lock(&smmu_domain->init_mutex);
-        BUG_ON(smmu_group->domain != smmu_domain);
-
-        smmu_group->ste.bypass = true;
-        if (IS_ERR_VALUE(arm_smmu_install_ste_for_group(smmu_group)))
-                dev_warn(dev, "failed to install bypass STE\n");
-
-        smmu_group->domain = NULL;
-        mutex_unlock(&smmu_domain->init_mutex);
-}
-
 static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
                         phys_addr_t paddr, size_t size, int prot)
 {
@@ -1943,7 +1935,6 @@ static struct iommu_ops arm_smmu_ops = {
         .domain_alloc           = arm_smmu_domain_alloc,
         .domain_free            = arm_smmu_domain_free,
         .attach_dev             = arm_smmu_attach_dev,
-        .detach_dev             = arm_smmu_detach_dev,
         .map                    = arm_smmu_map,
         .unmap                  = arm_smmu_unmap,
         .iova_to_phys           = arm_smmu_iova_to_phys,
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 7012531abe62..f21332a15040 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1131,6 +1131,16 @@ static void arm_smmu_domain_remove_master(struct arm_smmu_domain *smmu_domain,
         arm_smmu_master_free_smrs(smmu, cfg);
 }
 
+static void arm_smmu_detach_dev(struct device *dev,
+                                struct arm_smmu_master_cfg *cfg)
+{
+        struct iommu_domain *domain = dev->archdata.iommu;
+        struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+
+        dev->archdata.iommu = NULL;
+        arm_smmu_domain_remove_master(smmu_domain, cfg);
+}
+
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
         int ret;
@@ -1144,11 +1154,6 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
                 return -ENXIO;
         }
 
-        if (dev->archdata.iommu) {
-                dev_err(dev, "already attached to IOMMU domain\n");
-                return -EEXIST;
-        }
-
         /* Ensure that the domain is finalised */
         ret = arm_smmu_init_domain_context(domain, smmu);
         if (IS_ERR_VALUE(ret))
@@ -1170,25 +1175,16 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
         if (!cfg)
                 return -ENODEV;
 
+        /* Detach the dev from its current domain */
+        if (dev->archdata.iommu)
+                arm_smmu_detach_dev(dev, cfg);
+
         ret = arm_smmu_domain_add_master(smmu_domain, cfg);
         if (!ret)
                 dev->archdata.iommu = domain;
         return ret;
 }
 
-static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
-{
-        struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-        struct arm_smmu_master_cfg *cfg;
-
-        cfg = find_smmu_master_cfg(dev);
-        if (!cfg)
-                return;
-
-        dev->archdata.iommu = NULL;
-        arm_smmu_domain_remove_master(smmu_domain, cfg);
-}
-
 static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
                         phys_addr_t paddr, size_t size, int prot)
 {
@@ -1464,7 +1460,6 @@ static struct iommu_ops arm_smmu_ops = {
         .domain_alloc           = arm_smmu_domain_alloc,
         .domain_free            = arm_smmu_domain_free,
         .attach_dev             = arm_smmu_attach_dev,
-        .detach_dev             = arm_smmu_detach_dev,
         .map                    = arm_smmu_map,
         .unmap                  = arm_smmu_unmap,
         .map_sg                 = default_iommu_map_sg,