vfio iommu: Add blocking notifier to notify DMA_UNMAP

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 <kwankhede@nvidia.com>
Signed-off-by: Neo Jia <cjia@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio.c

@@ -1901,6 +1901,79 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
 }
 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
  */

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 <alex.williamson@redhat.com>"
@@ -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 = 0;
 
 	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;
 }
@@ -1553,6 +1583,22 @@ 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,
@@ -1563,6 +1609,8 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
 	.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)

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
  */