qemu/vdpa-always-start-CVQ-in-SVQ-mode-if-possible.patch

From e2e9aeaacdb28b6c2a1bfcfef09113dc9b26a420 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
Date: Thu, 15 Dec 2022 12:31:44 +0100
Subject: [PATCH] vdpa: always start CVQ in SVQ mode if possible
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Isolate control virtqueue in its own group, allowing to intercept control
commands but letting dataplane run totally passthrough to the guest.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20221215113144.322011-13-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: fangyi <eric.fangyi@huawei.com>
---
 hw/virtio/vhost-vdpa.c                       |   3 +-
 include/standard-headers/linux/vhost_types.h |   5 +
 linux-headers/linux/vhost.h                  |  14 +++
 net/vhost-vdpa.c                             | 110 ++++++++++++++++++-
 4 files changed, 130 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 6d0d85b733..8b44f5a7b8 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -641,7 +641,8 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
 {
     uint64_t features;
     uint64_t f = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
-        0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH;
+        0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
+        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID;
     int r;
 
     if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &features)) {
diff --git a/include/standard-headers/linux/vhost_types.h b/include/standard-headers/linux/vhost_types.h
index fa267e39d4..17833e320e 100644
--- a/include/standard-headers/linux/vhost_types.h
+++ b/include/standard-headers/linux/vhost_types.h
@@ -153,4 +153,9 @@ struct vhost_vdpa_iova_range {
 /* vhost-net should add virtio_net_hdr for RX, and strip for TX packets. */
 #define VHOST_NET_F_VIRTIO_NET_HDR 27
 
+/* IOTLB can accept address space identifier through V2 type of IOTLB
+ * message
+ */
+#define VHOST_BACKEND_F_IOTLB_ASID  0x3
+
 #endif
diff --git a/linux-headers/linux/vhost.h b/linux-headers/linux/vhost.h
index 5d99e7c242..b6ded7f831 100644
--- a/linux-headers/linux/vhost.h
+++ b/linux-headers/linux/vhost.h
@@ -157,4 +157,18 @@
 /* Get the count of all virtqueues */
 #define VHOST_VDPA_GET_VQS_COUNT	_IOR(VHOST_VIRTIO, 0x80, __u32)
 
+/* Get the group for a virtqueue: read index, write group in num,
+ * The virtqueue index is stored in the index field of
+ * vhost_vring_state. The group for this specific virtqueue is
+ * returned via num field of vhost_vring_state.
+ */
+#define VHOST_VDPA_GET_VRING_GROUP  _IOWR(VHOST_VIRTIO, 0x7B, \
+                                         struct vhost_vring_state)
+/* Set the ASID for a virtqueue group. The group index is stored in
+ * the index field of vhost_vring_state, the ASID associated with this
+ * group is stored at num field of vhost_vring_state.
+ */
+#define VHOST_VDPA_SET_GROUP_ASID   _IOW(VHOST_VIRTIO, 0x7C, \
+                                         struct vhost_vring_state)
+
 #endif
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 21fb89bb6b..24c4c2ef51 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -100,6 +100,8 @@ static const uint64_t vdpa_svq_device_features =
     BIT_ULL(VIRTIO_NET_F_RSC_EXT) |
     BIT_ULL(VIRTIO_NET_F_STANDBY);
 
+#define VHOST_VDPA_NET_CVQ_ASID 1
+
 VHostNetState *vhost_vdpa_get_vhost_net(NetClientState *nc)
 {
     VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
@@ -250,6 +252,40 @@ static NetClientInfo net_vhost_vdpa_info = {
         .check_peer_type = vhost_vdpa_check_peer_type,
 };
 
+static int64_t vhost_vdpa_get_vring_group(int device_fd, unsigned vq_index)
+{
+    struct vhost_vring_state state = {
+        .index = vq_index,
+    };
+    int r = ioctl(device_fd, VHOST_VDPA_GET_VRING_GROUP, &state);
+
+    if (unlikely(r < 0)) {
+        error_report("Cannot get VQ %u group: %s", vq_index,
+                     g_strerror(errno));
+        return r;
+    }
+
+    return state.num;
+}
+
+static int vhost_vdpa_set_address_space_id(struct vhost_vdpa *v,
+                                           unsigned vq_group,
+                                           unsigned asid_num)
+{
+    struct vhost_vring_state asid = {
+        .index = vq_group,
+        .num = asid_num,
+    };
+    int r;
+
+    r = ioctl(v->device_fd, VHOST_VDPA_SET_GROUP_ASID, &asid);
+    if (unlikely(r < 0)) {
+        error_report("Can't set vq group %u asid %u, errno=%d (%s)",
+                     asid.index, asid.num, errno, g_strerror(errno));
+    }
+    return r;
+}
+
 static void vhost_vdpa_cvq_unmap_buf(struct vhost_vdpa *v, void *addr)
 {
     VhostIOVATree *tree = v->iova_tree;
@@ -324,11 +360,75 @@ dma_map_err:
 static int vhost_vdpa_net_cvq_start(NetClientState *nc)
 {
     VhostVDPAState *s;
-    int r;
+    struct vhost_vdpa *v;
+    uint64_t backend_features;
+    int64_t cvq_group;
+    int cvq_index, r;
 
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
     s = DO_UPCAST(VhostVDPAState, nc, nc);
+    v = &s->vhost_vdpa;
+
+    v->shadow_data = s->always_svq;
+    v->shadow_vqs_enabled = s->always_svq;
+    s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
+
+    if (s->always_svq) {
+        /* SVQ is already configured for all virtqueues */
+        goto out;
+    }
+
+    /*
+     * If we early return in these cases SVQ will not be enabled. The migration
+     * will be blocked as long as vhost-vdpa backends will not offer _F_LOG.
+     *
+     * Calling VHOST_GET_BACKEND_FEATURES as they are not available in v->dev
+     * yet.
+     */
+    r = ioctl(v->device_fd, VHOST_GET_BACKEND_FEATURES, &backend_features);
+    if (unlikely(r < 0)) {
+        error_report("Cannot get vdpa backend_features: %s(%d)",
+            g_strerror(errno), errno);
+        return -1;
+    }
+    if (!(backend_features & VHOST_BACKEND_F_IOTLB_ASID) ||
+        !vhost_vdpa_net_valid_svq_features(v->dev->features, NULL)) {
+        return 0;
+    }
+
+    /*
+     * Check if all the virtqueues of the virtio device are in a different vq
+     * than the last vq. VQ group of last group passed in cvq_group.
+     */
+    cvq_index = v->dev->vq_index_end - 1;
+    cvq_group = vhost_vdpa_get_vring_group(v->device_fd, cvq_index);
+    if (unlikely(cvq_group < 0)) {
+        return cvq_group;
+    }
+    for (int i = 0; i < cvq_index; ++i) {
+        int64_t group = vhost_vdpa_get_vring_group(v->device_fd, i);
+
+        if (unlikely(group < 0)) {
+            return group;
+        }
+
+        if (group == cvq_group) {
+            return 0;
+        }
+    }
+
+    r = vhost_vdpa_set_address_space_id(v, cvq_group, VHOST_VDPA_NET_CVQ_ASID);
+    if (unlikely(r < 0)) {
+        return r;
+    }
+
+    v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
+                                       v->iova_range.last);
+    v->shadow_vqs_enabled = true;
+    s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
+
+out:
     if (!s->vhost_vdpa.shadow_vqs_enabled) {
         return 0;
     }
@@ -357,6 +457,14 @@ static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
     if (s->vhost_vdpa.shadow_vqs_enabled) {
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
+        if (!s->always_svq) {
+            /*
+             * If only the CVQ is shadowed we can delete this safely.
+             * If all the VQs are shadows this will be needed by the time the
+             * device is started again to register SVQ vrings and similar.
+             */
+            g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
+        }
     }
 }
 
-- 
2.27.0