[dpdk-dev] [PATCH v2] vhost: flush IOTLB cache on new mem table handling

[Maxime Coquelin]

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: sta...@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
Changes since v1:
- Fix indentation (Stephen)
- Fix double iotlb-lock lock

 lib/librte_vhost/iotlb.c      | 10 ++++++++--
 lib/librte_vhost/iotlb.h      |  2 +-
 lib/librte_vhost/vhost_user.c |  5 +++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/iotlb.c b/lib/librte_vhost/iotlb.c
index c11ebcaac..c6354fef7 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..a2d4c9ffc 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -813,6 +813,11 @@ 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++)
+                       vhost_user_iotlb_flush_all(dev->virtqueue[i]);
+
        dev->nr_guest_pages = 0;
        if (!dev->guest_pages) {
                dev->max_guest_pages = 8;
-- 
2.14.4