[dpdk-dev] [PATCH] vhost: flush IOTLB cache on new mem table handling

[Maxime Coquelin <maxime.coquelin@redhat.com>]

IOTLB entries contain the host virtual address of the guest
pages. When receiving a new VHOST_USER_SET_MEM_TABLE request,
the previous regions get unmapped, so the IOTLB entries, if any,
will be invalid. It does cause the vhost-user process to
segfault.

This patch introduces a new function to flush the IOTLB cache,
and call it as soon as the backend handles a VHOST_USER_SET_MEM
request.

Fixes: 69c90e98f483 ("vhost: enable IOMMU support")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/iotlb.c      | 10 ++++++++--
 lib/librte_vhost/iotlb.h      |  2 +-
 lib/librte_vhost/vhost_user.c | 11 +++++++++++
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/iotlb.c b/lib/librte_vhost/iotlb.c
index c11ebcaac..51beb110c 100644
--- a/lib/librte_vhost/iotlb.c
+++ b/lib/librte_vhost/iotlb.c
@@ -303,6 +303,13 @@ vhost_user_iotlb_cache_find(struct vhost_virtqueue *vq, uint64_t iova,
 	return vva;
 }
 
+void
+vhost_user_iotlb_flush_all(struct vhost_virtqueue *vq)
+{
+		vhost_user_iotlb_cache_remove_all(vq);
+		vhost_user_iotlb_pending_remove_all(vq);
+}
+
 int
 vhost_user_iotlb_init(struct virtio_net *dev, int vq_index)
 {
@@ -315,8 +322,7 @@ vhost_user_iotlb_init(struct virtio_net *dev, int vq_index)
 		 * The cache has already been initialized,
 		 * just drop all cached and pending entries.
 		 */
-		vhost_user_iotlb_cache_remove_all(vq);
-		vhost_user_iotlb_pending_remove_all(vq);
+		vhost_user_iotlb_flush_all(vq);
 	}
 
 #ifdef RTE_LIBRTE_VHOST_NUMA
diff --git a/lib/librte_vhost/iotlb.h b/lib/librte_vhost/iotlb.h
index e7083e37b..60b9e4c57 100644
--- a/lib/librte_vhost/iotlb.h
+++ b/lib/librte_vhost/iotlb.h
@@ -73,7 +73,7 @@ void vhost_user_iotlb_pending_insert(struct vhost_virtqueue *vq, uint64_t iova,
 						uint8_t perm);
 void vhost_user_iotlb_pending_remove(struct vhost_virtqueue *vq, uint64_t iova,
 						uint64_t size, uint8_t perm);
-
+void vhost_user_iotlb_flush_all(struct vhost_virtqueue *vq);
 int vhost_user_iotlb_init(struct virtio_net *dev, int vq_index);
 
 #endif /* _VHOST_IOTLB_H_ */
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index dc53ff712..d8cf33cd4 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -813,6 +813,17 @@ vhost_user_set_mem_table(struct virtio_net **pdev, struct VhostUserMsg *pmsg)
 		dev->mem = NULL;
 	}
 
+	/* Flush IOTLB cache as previous HVAs are now invalid */
+	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) {
+		for (i = 0; i < dev->nr_vring; i++) {
+			struct vhost_virtqueue *vq = dev->virtqueue[i];
+
+			vhost_user_iotlb_wr_lock(vq);
+			vhost_user_iotlb_flush_all(vq);
+			vhost_user_iotlb_wr_unlock(vq);
+		}
+	}
+
 	dev->nr_guest_pages = 0;
 	if (!dev->guest_pages) {
 		dev->max_guest_pages = 8;
-- 
2.14.4