[PATCH RFC v3 3/4] vhost-vdpa: should restore 1:1 dma mapping before detaching driver

[Si-Wei Liu <si-wei.liu@oracle.com>]

Devices with on-chip IOMMU may need to restore iotlb to 1:1 identity
mapping from IOVA to PA. Before vhost-vdpa is going away, give them
a chance to clean up and reset iotlb back to 1:1 identify mapping
mode. This is done so that any vdpa bus driver may start with 1:1
identity mapping by default.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
 drivers/vhost/vdpa.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index eabac06..71fbd559 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -131,6 +131,15 @@ static struct vhost_vdpa_as *vhost_vdpa_find_alloc_as(struct vhost_vdpa *v,
 	return vhost_vdpa_alloc_as(v, asid);
 }
 
+static void vhost_vdpa_reset_map(struct vhost_vdpa *v, u32 asid)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+
+	if (ops->reset_map)
+		ops->reset_map(vdpa, asid);
+}
+
 static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32 asid)
 {
 	struct vhost_vdpa_as *as = asid_to_as(v, asid);
@@ -140,6 +149,14 @@ static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32 asid)
 
 	hlist_del(&as->hash_link);
 	vhost_vdpa_iotlb_unmap(v, &as->iotlb, 0ULL, 0ULL - 1, asid);
+	/*
+	 * Devices with on-chip IOMMU need to restore iotlb
+	 * to 1:1 identity mapping before vhost-vdpa is going
+	 * to be removed and detached from the device. Give
+	 * them a chance to do so, as this cannot be done
+	 * efficiently via the whole-range unmap call above.
+	 */
+	vhost_vdpa_reset_map(v, asid);
 	kfree(as);
 
 	return 0;
-- 
1.8.3.1

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