[PATCH RFC 09/15] hw/virtio/vhost-shadow-virtqueue: specified vring placement

By default svq vrings are placed in an anonymous memory map. As svqs
will be leveraged to enable memory isolation in vhost-user, it is useful
to be able to place the vrings in a shared isolation memory region.

Adds the option to specify vring placement by providing a vring base
address before starting the svq.

Signed-off-by: Connor Kite <[email protected]>
---
 hw/virtio/vhost-shadow-virtqueue.c | 22 +++++++++++++++-------
 hw/virtio/vhost-shadow-virtqueue.h |  3 +++
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index eb86c1ee37..9e3c359f50 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -857,14 +857,21 @@ void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
 
     svq->vring.num = virtio_queue_get_num(vdev, virtio_get_queue_index(vq));
     svq->num_free = svq->vring.num;
-    svq->vring.desc = mmap(NULL, vhost_svq_driver_area_size(svq),
-                           PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,
-                           -1, 0);
     desc_size = sizeof(vring_desc_t) * svq->vring.num;
-    svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
-    svq->vring.used = mmap(NULL, vhost_svq_device_area_size(svq),
-                           PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,
-                           -1, 0);
+    if (svq->base_addr == NULL) {
+        svq->vring.desc = mmap(NULL, vhost_svq_driver_area_size(svq),
+                            PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,
+                            -1, 0);
+        svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
+        svq->vring.used = mmap(NULL, vhost_svq_device_area_size(svq),
+                            PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,
+                            -1, 0);
+    } else {
+        svq->vring.desc = (void *) svq->base_addr;
+        svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
+        svq->vring.used = (void *)((char *)svq->base_addr +
+                          vhost_svq_driver_area_size(svq));
+    }
     svq->desc_state = g_new0(SVQDescState, svq->vring.num);
     if (virtio_vdev_has_feature(svq->vdev, VIRTIO_F_IN_ORDER)) {
         svq->batch_last.id = VIRTIO_RING_NOT_IN_BATCH;
@@ -929,6 +936,7 @@ VhostShadowVirtqueue *vhost_svq_new(const VhostShadowVirtqueueOps *ops,
     event_notifier_init_fd(&svq->svq_kick, VHOST_FILE_UNBIND);
     svq->ops = ops;
     svq->ops_opaque = ops_opaque;
+    svq->base_addr = NULL;
     return svq;
 }
 
diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index ccfeee36d7..39f69e6455 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -148,6 +148,9 @@ typedef struct VhostShadowVirtqueue {
 
     /* Size of SVQ vring free descriptors */
     uint16_t num_free;
+
+    /* Location assigned to vrings if not in default anon memory map*/
+    hwaddr *base_addr;
 } VhostShadowVirtqueue;
 
 bool vhost_svq_valid_features(uint64_t features, Error **errp);

-- 
2.43.0