iommu/amd: Implement notifiers for IOMMUv2

Since pages are not pinned anymore we need notifications
when the VMM changes the page-tables. Use mmu_notifiers for
that.
Also use the task_exit notifier from the profiling subsystem
to shutdown all contexts related to this task.

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

2 files changed, 178 insertions, 11 deletions

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index e608a36bb0b1..6bea6962f8ee 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -62,7 +62,8 @@ config AMD_IOMMU_STATS
 
 config AMD_IOMMU_V2
         tristate "AMD IOMMU Version 2 driver (EXPERIMENTAL)"
-        depends on AMD_IOMMU && EXPERIMENTAL
+        depends on AMD_IOMMU && PROFILING && EXPERIMENTAL
+        select MMU_NOTIFIER
         ---help---
           This option enables support for the AMD IOMMUv2 features of the IOMMU
           hardware. Select this option if you want to use devices that support
diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 8804b2247694..abdb8396f89a 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -16,8 +16,10 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  */
 
+#include <linux/mmu_notifier.h>
 #include <linux/amd-iommu.h>
 #include <linux/mm_types.h>
+#include <linux/profile.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/iommu.h>
@@ -45,6 +47,7 @@ struct pasid_state {
         atomic_t count;                         /* Reference count */
         struct task_struct *task;               /* Task bound to this PASID */
         struct mm_struct *mm;                   /* mm_struct for the faults */
+        struct mmu_notifier mn;                 /* mmu_otifier handle */
         struct pri_queue pri[PRI_QUEUE_SIZE];   /* PRI tag states */
         struct device_state *device_state;      /* Link to our device_state */
         int pasid;                              /* PASID index */
@@ -85,8 +88,16 @@ static DEFINE_SPINLOCK(ps_lock);
 
 static struct workqueue_struct *iommu_wq;
 
+/*
+ * Empty page table - Used between
+ * mmu_notifier_invalidate_range_start and
+ * mmu_notifier_invalidate_range_end
+ */
+static u64 *empty_page_table;
+
 static void free_pasid_states(struct device_state *dev_state);
 static void unbind_pasid(struct device_state *dev_state, int pasid);
+static int task_exit(struct notifier_block *nb, unsigned long e, void *data);
 
 static u16 device_id(struct pci_dev *pdev)
 {
@@ -144,6 +155,11 @@ static void put_device_state_wait(struct device_state *dev_state)
 
         free_device_state(dev_state);
 }
+
+static struct notifier_block profile_nb = {
+        .notifier_call = task_exit,
+};
+
 static void link_pasid_state(struct pasid_state *pasid_state)
 {
         spin_lock(&ps_lock);
@@ -294,6 +310,23 @@ static void put_pasid_state_wait(struct pasid_state *pasid_state)
         free_pasid_state(pasid_state);
 }
 
+static void __unbind_pasid(struct pasid_state *pasid_state)
+{
+        struct iommu_domain *domain;
+
+        domain = pasid_state->device_state->domain;
+
+        amd_iommu_domain_clear_gcr3(domain, pasid_state->pasid);
+        clear_pasid_state(pasid_state->device_state, pasid_state->pasid);
+
+        /* Make sure no more pending faults are in the queue */
+        flush_workqueue(iommu_wq);
+
+        mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);
+
+        put_pasid_state(pasid_state); /* Reference taken in bind() function */
+}
+
 static void unbind_pasid(struct device_state *dev_state, int pasid)
 {
         struct pasid_state *pasid_state;
@@ -303,12 +336,8 @@ static void unbind_pasid(struct device_state *dev_state, int pasid)
                 return;
 
         unlink_pasid_state(pasid_state);
-
-        amd_iommu_domain_clear_gcr3(dev_state->domain, pasid);
-        clear_pasid_state(dev_state, pasid);
-
-        put_pasid_state(pasid_state); /* Reference taken in this function */
-        put_pasid_state_wait(pasid_state); /* Reference from bind() function */
+        __unbind_pasid(pasid_state);
+        put_pasid_state_wait(pasid_state); /* Reference taken in this function */
 }
 
 static void free_pasid_states_level1(struct pasid_state **tbl)
@@ -361,6 +390,83 @@ static void free_pasid_states(struct device_state *dev_state)
         free_page((unsigned long)dev_state->states);
 }
 
+static struct pasid_state *mn_to_state(struct mmu_notifier *mn)
+{
+        return container_of(mn, struct pasid_state, mn);
+}
+
+static void __mn_flush_page(struct mmu_notifier *mn,
+                            unsigned long address)
+{
+        struct pasid_state *pasid_state;
+        struct device_state *dev_state;
+
+        pasid_state = mn_to_state(mn);
+        dev_state   = pasid_state->device_state;
+
+        amd_iommu_flush_page(dev_state->domain, pasid_state->pasid, address);
+}
+
+static int mn_clear_flush_young(struct mmu_notifier *mn,
+                                struct mm_struct *mm,
+                                unsigned long address)
+{
+        __mn_flush_page(mn, address);
+
+        return 0;
+}
+
+static void mn_change_pte(struct mmu_notifier *mn,
+                          struct mm_struct *mm,
+                          unsigned long address,
+                          pte_t pte)
+{
+        __mn_flush_page(mn, address);
+}
+
+static void mn_invalidate_page(struct mmu_notifier *mn,
+                               struct mm_struct *mm,
+                               unsigned long address)
+{
+        __mn_flush_page(mn, address);
+}
+
+static void mn_invalidate_range_start(struct mmu_notifier *mn,
+                                      struct mm_struct *mm,
+                                      unsigned long start, unsigned long end)
+{
+        struct pasid_state *pasid_state;
+        struct device_state *dev_state;
+
+        pasid_state = mn_to_state(mn);
+        dev_state   = pasid_state->device_state;
+
+        amd_iommu_domain_set_gcr3(dev_state->domain, pasid_state->pasid,
+                                  __pa(empty_page_table));
+}
+
+static void mn_invalidate_range_end(struct mmu_notifier *mn,
+                                    struct mm_struct *mm,
+                                    unsigned long start, unsigned long end)
+{
+        struct pasid_state *pasid_state;
+        struct device_state *dev_state;
+
+        pasid_state = mn_to_state(mn);
+        dev_state   = pasid_state->device_state;
+
+        amd_iommu_domain_set_gcr3(dev_state->domain, pasid_state->pasid,
+                                  __pa(pasid_state->mm->pgd));
+}
+
+static struct mmu_notifier_ops iommu_mn = {
+        .clear_flush_young      = mn_clear_flush_young,
+        .change_pte             = mn_change_pte,
+        .invalidate_page        = mn_invalidate_page,
+        .invalidate_range_start = mn_invalidate_range_start,
+        .invalidate_range_end   = mn_invalidate_range_end,
+};
+
 static void set_pri_tag_status(struct pasid_state *pasid_state,
                                u16 tag, int status)
 {
@@ -475,6 +581,50 @@ static struct notifier_block ppr_nb = {
         .notifier_call = ppr_notifier,
 };
 
+static int task_exit(struct notifier_block *nb, unsigned long e, void *data)
+{
+        struct pasid_state *pasid_state;
+        struct task_struct *task;
+
+        task = data;
+
+        /*
+         * Using this notifier is a hack - but there is no other choice
+         * at the moment. What I really want is a sleeping notifier that
+         * is called when an MM goes down. But such a notifier doesn't
+         * exist yet. The notifier needs to sleep because it has to make
+         * sure that the device does not use the PASID and the address
+         * space anymore before it is destroyed. This includes waiting
+         * for pending PRI requests to pass the workqueue. The
+         * MMU-Notifiers would be a good fit, but they use RCU and so
+         * they are not allowed to sleep. Lets see how we can solve this
+         * in a more intelligent way in the future.
+         */
+again:
+        spin_lock(&ps_lock);
+        list_for_each_entry(pasid_state, &pasid_state_list, list) {
+                struct device_state *dev_state;
+                int pasid;
+
+                if (pasid_state->task != task)
+                        continue;
+
+                /* Drop Lock and unbind */
+                spin_unlock(&ps_lock);
+
+                dev_state = pasid_state->device_state;
+                pasid     = pasid_state->pasid;
+
+                unbind_pasid(dev_state, pasid);
+
+                /* Task may be in the list multiple times */
+                goto again;
+        }
+        spin_unlock(&ps_lock);
+
+        return NOTIFY_OK;
+}
+
 int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
                          struct task_struct *task)
 {
@@ -509,13 +659,16 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
         pasid_state->mm           = get_task_mm(task);
         pasid_state->device_state = dev_state;
         pasid_state->pasid        = pasid;
+        pasid_state->mn.ops       = &iommu_mn;
 
         if (pasid_state->mm == NULL)
                 goto out_free;
 
+        mmu_notifier_register(&pasid_state->mn, pasid_state->mm);
+
         ret = set_pasid_state(dev_state, pasid_state, pasid);
         if (ret)
-                goto out_free;
+                goto out_unregister;
 
         ret = amd_iommu_domain_set_gcr3(dev_state->domain, pasid,
                                         __pa(pasid_state->mm->pgd));
@@ -529,6 +682,9 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
 out_clear_state:
         clear_pasid_state(dev_state, pasid);
 
+out_unregister:
+        mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);
+
 out_free:
         free_pasid_state(pasid_state);
 
@@ -689,15 +845,22 @@ static int __init amd_iommu_v2_init(void)
 
         ret = -ENOMEM;
         iommu_wq = create_workqueue("amd_iommu_v2");
-        if (iommu_wq == NULL) {
-                ret = -ENOMEM;
+        if (iommu_wq == NULL)
                 goto out_free;
-        }
+
+        ret = -ENOMEM;
+        empty_page_table = (u64 *)get_zeroed_page(GFP_KERNEL);
+        if (empty_page_table == NULL)
+                goto out_destroy_wq;
 
         amd_iommu_register_ppr_notifier(&ppr_nb);
+        profile_event_register(PROFILE_TASK_EXIT, &profile_nb);
 
         return 0;
 
+out_destroy_wq:
+        destroy_workqueue(iommu_wq);
+
 out_free:
         free_pages((unsigned long)state_table, get_order(state_table_size));
 
@@ -710,6 +873,7 @@ static void __exit amd_iommu_v2_exit(void)
         size_t state_table_size;
         int i;
 
+        profile_event_unregister(PROFILE_TASK_EXIT, &profile_nb);
         amd_iommu_unregister_ppr_notifier(&ppr_nb);
 
         flush_workqueue(iommu_wq);
@@ -734,6 +898,8 @@ static void __exit amd_iommu_v2_exit(void)
 
         state_table_size = MAX_DEVICES * sizeof(struct device_state *);
         free_pages((unsigned long)state_table, get_order(state_table_size));
+
+        free_page((unsigned long)empty_page_table);
 }
 
 module_init(amd_iommu_v2_init);