x86/amd-iommu: Add device bind reference counting

This patch adds a reference count to each device to count
how often the device was bound to that domain. This is
important for single devices that act as an alias for a
number of others. These devices must stay bound to their
domains until all devices that alias to it are unbound from
the same domain.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 29 insertions, 8 deletions

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 3214e8806f9..f5db7d5e444 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -152,6 +152,8 @@ static int iommu_init_device(struct device *dev)
         if (pdev)
                 dev_data->alias = &pdev->dev;
 
+        atomic_set(&dev_data->bind, 0);
+
         dev->archdata.iommu = dev_data;
 
 
@@ -1403,10 +1405,13 @@ static int __attach_device(struct device *dev,
                 return -EBUSY;
 
         /* Do real assignment */
-        if (alias != devid &&
-            alias_data->domain == NULL) {
-                alias_data->domain = domain;
-                set_dte_entry(alias, domain);
+        if (alias != devid) {
+                if (alias_data->domain == NULL) {
+                        alias_data->domain = domain;
+                        set_dte_entry(alias, domain);
+                }
+
+                atomic_inc(&alias_data->bind);
         }
 
         if (dev_data->domain == NULL) {
@@ -1414,6 +1419,8 @@ static int __attach_device(struct device *dev,
                 set_dte_entry(devid, domain);
         }
 
+        atomic_inc(&dev_data->bind);
+
         /* ready */
         spin_unlock(&domain->lock);
 
@@ -1449,20 +1456,34 @@ static int attach_device(struct device *dev,
  */
 static void __detach_device(struct device *dev)
 {
-        u16 devid = get_device_id(dev);
+        u16 devid = get_device_id(dev), alias;
         struct amd_iommu *iommu = amd_iommu_rlookup_table[devid];
         struct iommu_dev_data *dev_data = get_dev_data(dev);
+        struct iommu_dev_data *alias_data;
 
         BUG_ON(!iommu);
 
-        clear_dte_entry(devid);
-        dev_data->domain = NULL;
+        devid = get_device_id(dev);
+        alias = get_device_id(dev_data->alias);
+
+        if (devid != alias) {
+                alias_data = get_dev_data(dev_data->alias);
+                if (atomic_dec_and_test(&alias_data->bind)) {
+                        clear_dte_entry(alias);
+                        alias_data->domain = NULL;
+                }
+        }
+
+        if (atomic_dec_and_test(&dev_data->bind)) {
+                clear_dte_entry(devid);
+                dev_data->domain = NULL;
+        }
 
         /*
          * If we run in passthrough mode the device must be assigned to the
          * passthrough domain if it is detached from any other domain
          */
-        if (iommu_pass_through)
+        if (iommu_pass_through && dev_data->domain == NULL)
                 __attach_device(dev, pt_domain);
 }