[PATCH] vhost: reduce memory footprint when IOMMU is disabled

[David Marchand]

If an application does not request IOMMU support, we can avoid
allocating a IOMMU pool.

This saves 112kB (IOTLB_CACHE_SIZE * sizeof(struct vhost_iotlb_entry))
per vq.

Signed-off-by: David Marchand <david.march...@redhat.com>
---
 lib/vhost/iotlb.c  | 20 +++++++++++---------
 lib/vhost/socket.c |  4 +++-
 lib/vhost/vhost.c  |  7 ++++++-
 lib/vhost/vhost.h  |  5 ++++-
 4 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/lib/vhost/iotlb.c b/lib/vhost/iotlb.c
index 2a78929e78..6a729e8804 100644
--- a/lib/vhost/iotlb.c
+++ b/lib/vhost/iotlb.c
@@ -341,16 +341,18 @@ vhost_user_iotlb_init(struct virtio_net *dev, struct 
vhost_virtqueue *vq)
        TAILQ_INIT(&vq->iotlb_list);
        TAILQ_INIT(&vq->iotlb_pending_list);
 
-       vq->iotlb_pool = rte_calloc_socket("iotlb", IOTLB_CACHE_SIZE,
-               sizeof(struct vhost_iotlb_entry), 0, socket);
-       if (!vq->iotlb_pool) {
-               VHOST_LOG_CONFIG(dev->ifname, ERR,
-                       "Failed to create IOTLB cache pool for vq %"PRIu32"\n",
-                       vq->index);
-               return -1;
+       if (dev->flags & VIRTIO_DEV_SUPPORT_IOMMU) {
+               vq->iotlb_pool = rte_calloc_socket("iotlb", IOTLB_CACHE_SIZE,
+                       sizeof(struct vhost_iotlb_entry), 0, socket);
+               if (!vq->iotlb_pool) {
+                       VHOST_LOG_CONFIG(dev->ifname, ERR,
+                               "Failed to create IOTLB cache pool for vq 
%"PRIu32"\n",
+                               vq->index);
+                       return -1;
+               }
+               for (i = 0; i < IOTLB_CACHE_SIZE; i++)
+                       vhost_user_iotlb_pool_put(vq, &vq->iotlb_pool[i]);
        }
-       for (i = 0; i < IOTLB_CACHE_SIZE; i++)
-               vhost_user_iotlb_pool_put(vq, &vq->iotlb_pool[i]);
 
        vq->iotlb_cache_nr = 0;
 
diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index a8df2d484a..608ae577fd 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -228,7 +228,8 @@ vhost_user_add_connection(int fd, struct vhost_user_socket 
*vsocket)
        vhost_set_ifname(vid, vsocket->path, size);
 
        vhost_setup_virtio_net(vid, vsocket->use_builtin_virtio_net,
-               vsocket->net_compliant_ol_flags, vsocket->stats_enabled);
+               vsocket->net_compliant_ol_flags, vsocket->stats_enabled,
+               vsocket->iommu_support);
 
        vhost_attach_vdpa_device(vid, vsocket->vdpa_dev);
 
@@ -905,6 +906,7 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
        vsocket->async_copy = flags & RTE_VHOST_USER_ASYNC_COPY;
        vsocket->net_compliant_ol_flags = flags & 
RTE_VHOST_USER_NET_COMPLIANT_OL_FLAGS;
        vsocket->stats_enabled = flags & RTE_VHOST_USER_NET_STATS_ENABLE;
+       vsocket->iommu_support = flags & RTE_VHOST_USER_IOMMU_SUPPORT;
 
        if (vsocket->async_copy &&
                (flags & (RTE_VHOST_USER_IOMMU_SUPPORT |
diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index aa671f47a3..9e5e69f72d 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -771,7 +771,8 @@ vhost_set_ifname(int vid, const char *if_name, unsigned int 
if_len)
 }
 
 void
-vhost_setup_virtio_net(int vid, bool enable, bool compliant_ol_flags, bool 
stats_enabled)
+vhost_setup_virtio_net(int vid, bool enable, bool compliant_ol_flags, bool 
stats_enabled,
+       bool support_iommu)
 {
        struct virtio_net *dev = get_device(vid);
 
@@ -790,6 +791,10 @@ vhost_setup_virtio_net(int vid, bool enable, bool 
compliant_ol_flags, bool stats
                dev->flags |= VIRTIO_DEV_STATS_ENABLED;
        else
                dev->flags &= ~VIRTIO_DEV_STATS_ENABLED;
+       if (support_iommu)
+               dev->flags |= VIRTIO_DEV_SUPPORT_IOMMU;
+       else
+               dev->flags &= ~VIRTIO_DEV_SUPPORT_IOMMU;
 }
 
 void
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index 782d916ae0..3da6f217fd 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -37,6 +37,8 @@
 #define VIRTIO_DEV_LEGACY_OL_FLAGS ((uint32_t)1 << 5)
 /*  Used to indicate the application has requested statistics collection */
 #define VIRTIO_DEV_STATS_ENABLED ((uint32_t)1 << 6)
+/*  Used to indicate the application has requested iommu support */
+#define VIRTIO_DEV_SUPPORT_IOMMU ((uint32_t)1 << 7)
 
 /* Backend value set by guest. */
 #define VIRTIO_DEV_STOPPED -1
@@ -803,7 +805,8 @@ int alloc_vring_queue(struct virtio_net *dev, uint32_t 
vring_idx);
 void vhost_attach_vdpa_device(int vid, struct rte_vdpa_device *dev);
 
 void vhost_set_ifname(int, const char *if_name, unsigned int if_len);
-void vhost_setup_virtio_net(int vid, bool enable, bool legacy_ol_flags, bool 
stats_enabled);
+void vhost_setup_virtio_net(int vid, bool enable, bool legacy_ol_flags, bool 
stats_enabled,
+       bool support_iommu);
 void vhost_enable_extbuf(int vid);
 void vhost_enable_linearbuf(int vid);
 int vhost_enable_guest_notification(struct virtio_net *dev,
-- 
2.37.3