Re: [Qemu-devel] [PATCH v14 11/22] vfio iommu: Add blocking notifier to notify DMA_UNMAP

[Kirti Wankhede]

Added blocking notifier to IOMMU TYPE1 driver to notify vendor drivers
about DMA_UNMAP.
Exported two APIs vfio_register_notifier() and vfio_unregister_notifier().
Notifier should be registered, if external user wants to use
vfio_pin_pages()/vfio_unpin_pages() APIs to pin/unpin pages.
Vendor driver should use VFIO_IOMMU_NOTIFY_DMA_UNMAP action to invalidate
mappings.

Signed-off-by: Kirti Wankhede <address@hidden>
Signed-off-by: Neo Jia <address@hidden>
Change-Id: I5910d0024d6be87f3e8d3e0ca0eaeaaa0b17f271
---
 drivers/vfio/vfio.c             | 73 ++++++++++++++++++++++++++++++++++++++++
 drivers/vfio/vfio_iommu_type1.c | 74 +++++++++++++++++++++++++++++++++--------
 include/linux/vfio.h            | 12 +++++++
 3 files changed, 146 insertions(+), 13 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index bd36c16b0ef2..301eed07a0ab 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1901,6 +1901,79 @@ err_unpin_pages:
 }
 EXPORT_SYMBOL(vfio_unpin_pages);
 
+int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
+{
+       struct vfio_container *container;
+       struct vfio_group *group;
+       struct vfio_iommu_driver *driver;
+       int ret;
+
+       if (!dev || !nb)
+               return -EINVAL;
+
+       group = vfio_group_get_from_dev(dev);
+       if (IS_ERR(group))
+               return PTR_ERR(group);
+
+       ret = vfio_group_add_container_user(group);
+       if (ret)
+               goto err_register_nb;
+
+       container = group->container;
+       down_read(&container->group_lock);
+
+       driver = container->iommu_driver;
+       if (likely(driver && driver->ops->register_notifier))
+               ret = driver->ops->register_notifier(container->iommu_data, nb);
+       else
+               ret = -ENOTTY;
+
+       up_read(&container->group_lock);
+       vfio_group_try_dissolve_container(group);
+
+err_register_nb:
+       vfio_group_put(group);
+       return ret;
+}
+EXPORT_SYMBOL(vfio_register_notifier);
+
+int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
+{
+       struct vfio_container *container;
+       struct vfio_group *group;
+       struct vfio_iommu_driver *driver;
+       int ret;
+
+       if (!dev || !nb)
+               return -EINVAL;
+
+       group = vfio_group_get_from_dev(dev);
+       if (IS_ERR(group))
+               return PTR_ERR(group);
+
+       ret = vfio_group_add_container_user(group);
+       if (ret)
+               goto err_unregister_nb;
+
+       container = group->container;
+       down_read(&container->group_lock);
+
+       driver = container->iommu_driver;
+       if (likely(driver && driver->ops->unregister_notifier))
+               ret = driver->ops->unregister_notifier(container->iommu_data,
+                                                      nb);
+       else
+               ret = -ENOTTY;
+
+       up_read(&container->group_lock);
+       vfio_group_try_dissolve_container(group);
+
+err_unregister_nb:
+       vfio_group_put(group);
+       return ret;
+}
+EXPORT_SYMBOL(vfio_unregister_notifier);
+
 /**
  * Module/class support
  */
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index db0901f8a149..511c517bae15 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -38,6 +38,7 @@
 #include <linux/workqueue.h>
 #include <linux/pid_namespace.h>
 #include <linux/mdev.h>
+#include <linux/notifier.h>
 
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <address@hidden>"
@@ -60,6 +61,7 @@ struct vfio_iommu {
        struct vfio_domain      *external_domain; /* domain for external user */
        struct mutex            lock;
        struct rb_root          dma_list;
+       struct blocking_notifier_head notifier;
        bool                    v2;
        bool                    nesting;
 };
@@ -561,7 +563,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 
        mutex_lock(&iommu->lock);
 
-       if (!iommu->external_domain) {
+       /* Fail if notifier list is empty */
+       if ((!iommu->external_domain) || (!iommu->notifier.head)) {
                ret = -EINVAL;
                goto pin_done;
        }
@@ -776,9 +779,9 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
                             struct vfio_iommu_type1_dma_unmap *unmap)
 {
        uint64_t mask;
-       struct vfio_dma *dma;
+       struct vfio_dma *dma, *dma_last = NULL;
        size_t unmapped = 0;
-       int ret = 0;
+       int ret = 0, retries;
 
        mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
 
@@ -788,7 +791,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
                return -EINVAL;
 
        WARN_ON(mask & PAGE_MASK);
-
+again:
        mutex_lock(&iommu->lock);
 
        /*
@@ -844,6 +847,32 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
                 */
                if (dma->task->mm != current->mm)
                        break;
+
+               if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
+                       struct vfio_iommu_type1_dma_unmap nb_unmap;
+
+                       if (dma_last == dma) {
+                               BUG_ON(++retries > 10);
+                       } else {
+                               dma_last = dma;
+                               retries = 0;
+                       }
+
+                       nb_unmap.iova = dma->iova;
+                       nb_unmap.size = dma->size;
+
+                       /*
+                        * Notify anyone (mdev vendor drivers) to invalidate and
+                        * unmap iovas within the range we're about to unmap.
+                        * Vendor drivers MUST unpin pages in response to an
+                        * invalidation.
+                        */
+                       mutex_unlock(&iommu->lock);
+                       blocking_notifier_call_chain(&iommu->notifier,
+                                                   VFIO_IOMMU_NOTIFY_DMA_UNMAP,
+                                                   &nb_unmap);
+                       goto again;
+               }
                unmapped += dma->size;
                vfio_remove_dma(iommu, dma);
        }
@@ -1419,6 +1448,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
        INIT_LIST_HEAD(&iommu->domain_list);
        iommu->dma_list = RB_ROOT;
        mutex_init(&iommu->lock);
+       BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
 
        return iommu;
 }
@@ -1553,16 +1583,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
        return -ENOTTY;
 }
 
+static int vfio_iommu_type1_register_notifier(void *iommu_data,
+                                             struct notifier_block *nb)
+{
+       struct vfio_iommu *iommu = iommu_data;
+
+       return blocking_notifier_chain_register(&iommu->notifier, nb);
+}
+
+static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
+                                               struct notifier_block *nb)
+{
+       struct vfio_iommu *iommu = iommu_data;
+
+       return blocking_notifier_chain_unregister(&iommu->notifier, nb);
+}
+
 static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
-       .name           = "vfio-iommu-type1",
-       .owner          = THIS_MODULE,
-       .open           = vfio_iommu_type1_open,
-       .release        = vfio_iommu_type1_release,
-       .ioctl          = vfio_iommu_type1_ioctl,
-       .attach_group   = vfio_iommu_type1_attach_group,
-       .detach_group   = vfio_iommu_type1_detach_group,
-       .pin_pages      = vfio_iommu_type1_pin_pages,
-       .unpin_pages    = vfio_iommu_type1_unpin_pages,
+       .name                   = "vfio-iommu-type1",
+       .owner                  = THIS_MODULE,
+       .open                   = vfio_iommu_type1_open,
+       .release                = vfio_iommu_type1_release,
+       .ioctl                  = vfio_iommu_type1_ioctl,
+       .attach_group           = vfio_iommu_type1_attach_group,
+       .detach_group           = vfio_iommu_type1_detach_group,
+       .pin_pages              = vfio_iommu_type1_pin_pages,
+       .unpin_pages            = vfio_iommu_type1_unpin_pages,
+       .register_notifier      = vfio_iommu_type1_register_notifier,
+       .unregister_notifier    = vfio_iommu_type1_unregister_notifier,
 };
 
 static int __init vfio_iommu_type1_init(void)
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 3c862a030029..6ab13f7e2920 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -80,6 +80,10 @@ struct vfio_iommu_driver_ops {
                                     unsigned long *phys_pfn);
        int             (*unpin_pages)(void *iommu_data,
                                       unsigned long *user_pfn, int npage);
+       int             (*register_notifier)(void *iommu_data,
+                                            struct notifier_block *nb);
+       int             (*unregister_notifier)(void *iommu_data,
+                                              struct notifier_block *nb);
 };
 
 extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
@@ -103,6 +107,14 @@ extern int vfio_pin_pages(struct device *dev, unsigned 
long *user_pfn,
 extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
                            int npage);
 
+#define VFIO_IOMMU_NOTIFY_DMA_UNMAP    (1)
+
+extern int vfio_register_notifier(struct device *dev,
+                                 struct notifier_block *nb);
+
+extern int vfio_unregister_notifier(struct device *dev,
+                                   struct notifier_block *nb);
+
 /*
  * Sub-module helpers
  */
-- 
2.7.0