[PATCH 10/40] vdpa: assign svq descriptors a separate ASID when possible

[Si-Wei Liu]

When backend supports the VHOST_BACKEND_F_DESC_ASID feature
and all the data vqs can support one or more descriptor group
to host SVQ vrings and descriptors, we assign them a different
ASID than where its buffers reside in guest memory address
space. With this dedicated ASID for SVQs, the IOVA for what
vdpa device may care effectively becomes the GPA, thus there's
no need to translate IOVA address. For this reason, shadow_data
can be turned off accordingly. It doesn't mean the SVQ is not
enabled, but just that the translation is not needed from iova
tree perspective.

We can reuse CVQ's address space ID to host SVQ descriptors
because both CVQ and SVQ are emulated in the same QEMU
process, which will share the same VA address space.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
 hw/virtio/vhost-vdpa.c |  5 ++++-
 net/vhost-vdpa.c       | 57 ++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 24844b5..30dff95 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -627,6 +627,7 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void 
*opaque, Error **errp)
     uint64_t qemu_backend_features = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
                                      0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
                                      0x1ULL << VHOST_BACKEND_F_IOTLB_ASID |
+                                     0x1ULL << VHOST_BACKEND_F_DESC_ASID |
                                      0x1ULL << VHOST_BACKEND_F_SUSPEND;
     int ret;
 
@@ -1249,7 +1250,9 @@ static bool vhost_vdpa_svqs_start(struct vhost_dev *dev)
             goto err;
         }
 
-        vhost_svq_start(svq, dev->vdev, vq, v->shared->iova_tree);
+        vhost_svq_start(svq, dev->vdev, vq,
+                        v->desc_group >= 0 && v->address_space_id ?
+                        NULL : v->shared->iova_tree);
         ok = vhost_vdpa_svq_map_rings(dev, svq, &addr, &err);
         if (unlikely(!ok)) {
             goto err_map;
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 2555897..aebaa53 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -366,20 +366,50 @@ static int vhost_vdpa_set_address_space_id(struct 
vhost_vdpa *v,
 static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
+    int r;
 
     migration_add_notifier(&s->migration_state,
                            vdpa_net_migration_state_notifier);
 
+    if (!v->shadow_vqs_enabled) {
+        if (v->desc_group >= 0 &&
+            v->address_space_id != VHOST_VDPA_GUEST_PA_ASID) {
+            vhost_vdpa_set_address_space_id(v, v->desc_group,
+                                            VHOST_VDPA_GUEST_PA_ASID);
+            s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
+        }
+        return;
+    }
+
     /* iova_tree may be initialized by vhost_vdpa_net_load_setup */
-    if (v->shadow_vqs_enabled && !v->shared->iova_tree) {
+    if (!v->shared->iova_tree) {
         v->shared->iova_tree = vhost_iova_tree_new(v->shared->iova_range.first,
                                                    v->shared->iova_range.last);
     }
+
+    if (s->always_svq || v->desc_group < 0) {
+        return;
+    }
+
+    r = vhost_vdpa_set_address_space_id(v, v->desc_group,
+                                        VHOST_VDPA_NET_CVQ_ASID);
+    if (unlikely(r < 0)) {
+        /* The other data vqs should also fall back to using the same ASID */
+        s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
+        return;
+    }
+
+    /* No translation needed on data SVQ when descriptor group is used */
+    s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
+    s->vhost_vdpa.shared->shadow_data = false;
+    return;
 }
 
 static int vhost_vdpa_net_data_start(NetClientState *nc)
 {
     VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
+    VhostVDPAState *s0 = vhost_vdpa_net_first_nc_vdpa(s);
+
     struct vhost_vdpa *v = &s->vhost_vdpa;
 
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
@@ -397,6 +427,18 @@ static int vhost_vdpa_net_data_start(NetClientState *nc)
         return 0;
     }
 
+    if (v->desc_group >= 0 && v->desc_group != s0->vhost_vdpa.desc_group) {
+        unsigned asid;
+        asid = v->shadow_vqs_enabled ?
+            s0->vhost_vdpa.address_space_id : VHOST_VDPA_GUEST_PA_ASID;
+        if (asid != s->vhost_vdpa.address_space_id) {
+            vhost_vdpa_set_address_space_id(v, v->desc_group, asid);
+        }
+        s->vhost_vdpa.address_space_id = asid;
+    } else {
+        s->vhost_vdpa.address_space_id = s0->vhost_vdpa.address_space_id;
+    }
+
     return 0;
 }
 
@@ -603,13 +645,19 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
         return 0;
     }
 
-    if (!s->cvq_isolated) {
+    if (!s->cvq_isolated && v->desc_group < 0) {
+        if (s0->vhost_vdpa.shadow_vqs_enabled &&
+            s0->vhost_vdpa.desc_group >= 0 &&
+            s0->vhost_vdpa.address_space_id) {
+            v->shadow_vqs_enabled = false;
+        }
         return 0;
     }
 
-    cvq_group = vhost_vdpa_get_vring_group(v->shared->device_fd,
+    cvq_group = s->cvq_isolated ?
+                vhost_vdpa_get_vring_group(v->shared->device_fd,
                                            v->dev->vq_index_end - 1,
-                                           &err);
+                                           &err) : v->desc_group;
     if (unlikely(cvq_group < 0)) {
         error_report_err(err);
         return cvq_group;
@@ -1840,6 +1888,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState 
*peer,
     s->always_svq = svq;
     s->migration_state.notify = NULL;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
+    s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
     if (queue_pair_index == 0) {
         vhost_vdpa_net_valid_svq_features(features,
                                           &s->vhost_vdpa.migration_blocker);
-- 
1.8.3.1