[RFC v3 3/8] vfio: Reclaim PASIDs when application is down

Liu, Yi L
2020-01-29T12:06:59Z

From: Liu Yi L <yi.l.liu@intel.com>

When userspace application is down, kernel should reclaim the PASIDs
allocated for this application to avoid PASID leak. This patch adds
a PASID list in vfio_mm structure to track the allocated PASIDs. The
PASID reclaim will be triggered when last vfio container is released.

Previous discussions:
https://patchwork.kernel.org/patch/11209429/

Cc: Kevin Tian <kevin.tian@intel.com>
CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
---
drivers/vfio/vfio.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++---
include/linux/vfio.h | 6 ++++++
2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c43c757..425d60a 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -2148,15 +2148,31 @@ static struct vfio_mm *vfio_create_mm(struct mm_struct *mm)
vmm->pasid_quota = VFIO_DEFAULT_PASID_QUOTA;
vmm->pasid_count = 0;
mutex_init(&vmm->pasid_lock);
+ INIT_LIST_HEAD(&vmm->pasid_list);

list_add(&vmm->vfio_next, &vfio.vfio_mm_list);

return vmm;
}

+static void vfio_mm_reclaim_pasid(struct vfio_mm *vmm)
+{
+ struct pasid_node *pnode, *tmp;
+
+ mutex_lock(&vmm->pasid_lock);
+ list_for_each_entry_safe(pnode, tmp, &vmm->pasid_list, next) {
+ pr_info("%s, reclaim pasid: %u\n", __func__, pnode->pasid);
+ list_del(&pnode->next);
+ ioasid_free(pnode->pasid);
+ kfree(pnode);
+ }
+ mutex_unlock(&vmm->pasid_lock);
+}
+
static void vfio_mm_unlock_and_free(struct vfio_mm *vmm)
{
mutex_unlock(&vfio.vfio_mm_lock);
+ vfio_mm_reclaim_pasid(vmm);
kfree(vmm);
}

@@ -2204,6 +2220,39 @@ struct vfio_mm *vfio_mm_get_from_task(struct task_struct *task)
}
EXPORT_SYMBOL_GPL(vfio_mm_get_from_task);

+/**
+ * Caller should hold vmm->pasid_lock
+ */
+static int vfio_mm_insert_pasid_node(struct vfio_mm *vmm, u32 pasid)
+{
+ struct pasid_node *pnode;
+
+ pnode = kzalloc(sizeof(*pnode), GFP_KERNEL);
+ if (!pnode)
+ return -ENOMEM;
+ pnode->pasid = pasid;
+ list_add(&pnode->next, &vmm->pasid_list);
+
+ return 0;
+}
+
+/**
+ * Caller should hold vmm->pasid_lock
+ */
+static void vfio_mm_remove_pasid_node(struct vfio_mm *vmm, u32 pasid)
+{
+ struct pasid_node *pnode, *tmp;
+
+ list_for_each_entry_safe(pnode, tmp, &vmm->pasid_list, next) {
+ if (pnode->pasid == pasid) {
+ list_del(&pnode->next);
+ kfree(pnode);
+ break;
+ }
+ }
+
+}
+
int vfio_mm_pasid_alloc(struct vfio_mm *vmm, int min, int max)
{
ioasid_t pasid;
@@ -2221,9 +2270,15 @@ int vfio_mm_pasid_alloc(struct vfio_mm *vmm, int min, int max)
ret = -ENOSPC;
goto out_unlock;
}
- vmm->pasid_count++;

- ret = pasid;
+ if (vfio_mm_insert_pasid_node(vmm, pasid)) {
+ ret = -ENOSPC;
+ ioasid_free(pasid);
+ } else {
+ ret = pasid;
+ vmm->pasid_count++;
+ }
+
out_unlock:
mutex_unlock(&vmm->pasid_lock);
return ret;
@@ -2243,7 +2298,7 @@ int vfio_mm_pasid_free(struct vfio_mm *vmm, ioasid_t pasid)
goto out_unlock;
}
ioasid_free(pasid);
-
+ vfio_mm_remove_pasid_node(vmm, pasid);
vmm->pasid_count--;
out_unlock:
mutex_unlock(&vmm->pasid_lock);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index b6c9c8c..a2ea7e0 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -89,12 +89,18 @@ extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
extern void vfio_unregister_iommu_driver(
const struct vfio_iommu_driver_ops *ops);

+struct pasid_node {
+ u32 pasid;
+ struct list_head next;
+};
+
#define VFIO_DEFAULT_PASID_QUOTA 1000
struct vfio_mm {
struct kref kref;
struct mutex pasid_lock;
int pasid_quota;
int pasid_count;
+ struct list_head pasid_list;
struct mm_struct *mm;
struct list_head vfio_next;
};
--
2.7.4