[RFC v7] virtio/vsock: add two more queues for datagram types

[Jiang Wang]

Datagram sockets are connectionless and unreliable.
The sender does not know the capacity of the receiver
and may send more packets than the receiver can handle.

Add two more dedicate virtqueues for datagram sockets,
so that it will not unfairly steal resources from
stream and future connection-oriented sockets.

The two new virtqueues are enabled by default and will
be removed if the guest does not support. This will help
migration work.

btw: enable_dgram argument in vhost_vsock_common_realize
is redundant for now, but will be used later when we
want to disable DGRAM feature bit for old versions.

Signed-off-by: Jiang Wang <jiang.wang@bytedance.com>
---
v1 -> v2: use qemu cmd option to control number of queues,
        removed configuration settings for dgram.
v2 -> v3: use ioctl to get features and decide number of
        virt queues, instead of qemu cmd option.
v3 -> v4: change DGRAM feature bit value to 2. Add an argument
        in vhost_vsock_common_realize to indicate dgram is supported or not.
v4 -> v5: don't open dev to get vhostfd. Removed leftover definition of
        enable_dgram
v5 -> v6: fix style errors. Imporve error handling of
        vhost_vsock_dgram_supported. Rename MAX_VQS_WITH_DGRAM and another one.
v6 -> v7: Always enable dgram for vhost-user and vhost kernel.
        Delete unused virtqueues at the beginning of 
        vhost_vsock_common_start for migration. Otherwise, migration will fail.

 hw/virtio/vhost-user-vsock.c                  |  2 +-
 hw/virtio/vhost-vsock-common.c                | 32 +++++++++++++++++--
 hw/virtio/vhost-vsock.c                       |  6 +++-
 include/hw/virtio/vhost-vsock-common.h        |  6 ++--
 include/hw/virtio/vhost-vsock.h               |  3 ++
 include/standard-headers/linux/virtio_vsock.h |  1 +
 6 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
index 6095ed7349..9823a2f3bd 100644
--- a/hw/virtio/vhost-user-vsock.c
+++ b/hw/virtio/vhost-user-vsock.c
@@ -105,7 +105,7 @@ static void vuv_device_realize(DeviceState *dev, Error 
**errp)
         return;
     }
 
-    vhost_vsock_common_realize(vdev, "vhost-user-vsock");
+    vhost_vsock_common_realize(vdev, "vhost-user-vsock", true);
 
     vhost_dev_set_config_notifier(&vvc->vhost_dev, &vsock_ops);
 
diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
index 4ad6e234ad..7d89b4d242 100644
--- a/hw/virtio/vhost-vsock-common.c
+++ b/hw/virtio/vhost-vsock-common.c
@@ -26,6 +26,18 @@ int vhost_vsock_common_start(VirtIODevice *vdev)
     int ret;
     int i;
 
+    if (!virtio_has_feature(vdev->guest_features, VIRTIO_VSOCK_F_DGRAM)) {
+        struct vhost_virtqueue *vqs;
+        virtio_delete_queue(vvc->dgram_recv_vq);
+        virtio_delete_queue(vvc->dgram_trans_vq);
+
+        vqs = vvc->vhost_dev.vqs;
+        vvc->vhost_dev.nvqs = MAX_VQS_WITHOUT_DGRAM;
+        vvc->vhost_dev.vqs = g_new0(struct vhost_virtqueue,
+                                   vvc->vhost_dev.nvqs);
+        g_free(vqs);
+    }
+
     if (!k->set_guest_notifiers) {
         error_report("binding does not support guest notifiers");
         return -ENOSYS;
@@ -196,9 +208,11 @@ int vhost_vsock_common_post_load(void *opaque, int 
version_id)
     return 0;
 }
 
-void vhost_vsock_common_realize(VirtIODevice *vdev, const char *name)
+void vhost_vsock_common_realize(VirtIODevice *vdev, const char *name,
+                               bool enable_dgram)
 {
     VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
+    int nvqs = MAX_VQS_WITH_DGRAM;
 
     virtio_init(vdev, name, VIRTIO_ID_VSOCK,
                 sizeof(struct virtio_vsock_config));
@@ -209,12 +223,17 @@ void vhost_vsock_common_realize(VirtIODevice *vdev, const 
char *name)
     vvc->trans_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
                                        vhost_vsock_common_handle_output);
 
+    vvc->dgram_recv_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
+                                          vhost_vsock_common_handle_output);
+    vvc->dgram_trans_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
+                                          vhost_vsock_common_handle_output);
+
     /* The event queue belongs to QEMU */
     vvc->event_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
                                        vhost_vsock_common_handle_output);
 
-    vvc->vhost_dev.nvqs = ARRAY_SIZE(vvc->vhost_vqs);
-    vvc->vhost_dev.vqs = vvc->vhost_vqs;
+    vvc->vhost_dev.nvqs = nvqs;
+    vvc->vhost_dev.vqs = g_new0(struct vhost_virtqueue, vvc->vhost_dev.nvqs);
 
     vvc->post_load_timer = NULL;
 }
@@ -227,6 +246,13 @@ void vhost_vsock_common_unrealize(VirtIODevice *vdev)
 
     virtio_delete_queue(vvc->recv_vq);
     virtio_delete_queue(vvc->trans_vq);
+    if (vvc->vhost_dev.nvqs == MAX_VQS_WITH_DGRAM) {
+        virtio_delete_queue(vvc->dgram_recv_vq);
+        virtio_delete_queue(vvc->dgram_trans_vq);
+    }
+
+    g_free(vvc->vhost_dev.vqs);
+
     virtio_delete_queue(vvc->event_vq);
     virtio_cleanup(vdev);
 }
diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
index 1b1a5c70ed..6e315ecf23 100644
--- a/hw/virtio/vhost-vsock.c
+++ b/hw/virtio/vhost-vsock.c
@@ -23,6 +23,7 @@
 
 const int feature_bits[] = {
     VIRTIO_VSOCK_F_SEQPACKET,
+    VIRTIO_VSOCK_F_DGRAM,
     VHOST_INVALID_FEATURE_BIT
 };
 
@@ -116,6 +117,9 @@ static uint64_t vhost_vsock_get_features(VirtIODevice *vdev,
     VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
 
     virtio_add_feature(&requested_features, VIRTIO_VSOCK_F_SEQPACKET);
+    if (vvc->vhost_dev.nvqs == MAX_VQS_WITH_DGRAM) {
+        virtio_add_feature(&requested_features, VIRTIO_VSOCK_F_DGRAM);
+    }
     return vhost_get_features(&vvc->vhost_dev, feature_bits,
                                 requested_features);
 }
@@ -175,7 +179,7 @@ static void vhost_vsock_device_realize(DeviceState *dev, 
Error **errp)
         qemu_set_nonblock(vhostfd);
     }
 
-    vhost_vsock_common_realize(vdev, "vhost-vsock");
+    vhost_vsock_common_realize(vdev, "vhost-vsock", true);
 
     ret = vhost_dev_init(&vvc->vhost_dev, (void *)(uintptr_t)vhostfd,
                          VHOST_BACKEND_TYPE_KERNEL, 0, errp);
diff --git a/include/hw/virtio/vhost-vsock-common.h 
b/include/hw/virtio/vhost-vsock-common.h
index e412b5ee98..80151aee35 100644
--- a/include/hw/virtio/vhost-vsock-common.h
+++ b/include/hw/virtio/vhost-vsock-common.h
@@ -27,12 +27,13 @@ enum {
 struct VHostVSockCommon {
     VirtIODevice parent;
 
-    struct vhost_virtqueue vhost_vqs[2];
     struct vhost_dev vhost_dev;
 
     VirtQueue *event_vq;
     VirtQueue *recv_vq;
     VirtQueue *trans_vq;
+    VirtQueue *dgram_recv_vq;
+    VirtQueue *dgram_trans_vq;
 
     QEMUTimer *post_load_timer;
 };
@@ -41,7 +42,8 @@ int vhost_vsock_common_start(VirtIODevice *vdev);
 void vhost_vsock_common_stop(VirtIODevice *vdev);
 int vhost_vsock_common_pre_save(void *opaque);
 int vhost_vsock_common_post_load(void *opaque, int version_id);
-void vhost_vsock_common_realize(VirtIODevice *vdev, const char *name);
+void vhost_vsock_common_realize(VirtIODevice *vdev, const char *name,
+                                bool enable_dgram);
 void vhost_vsock_common_unrealize(VirtIODevice *vdev);
 
 #endif /* _QEMU_VHOST_VSOCK_COMMON_H */
diff --git a/include/hw/virtio/vhost-vsock.h b/include/hw/virtio/vhost-vsock.h
index 84f4e727c7..7d16c0e218 100644
--- a/include/hw/virtio/vhost-vsock.h
+++ b/include/hw/virtio/vhost-vsock.h
@@ -33,4 +33,7 @@ struct VHostVSock {
     /*< public >*/
 };
 
+#define MAX_VQS_WITHOUT_DGRAM 2
+#define MAX_VQS_WITH_DGRAM 4
+
 #endif /* QEMU_VHOST_VSOCK_H */
diff --git a/include/standard-headers/linux/virtio_vsock.h 
b/include/standard-headers/linux/virtio_vsock.h
index 3a23488e42..7e35acf3d4 100644
--- a/include/standard-headers/linux/virtio_vsock.h
+++ b/include/standard-headers/linux/virtio_vsock.h
@@ -40,6 +40,7 @@
 
 /* The feature bitmap for virtio vsock */
 #define VIRTIO_VSOCK_F_SEQPACKET       1       /* SOCK_SEQPACKET supported */
+#define VIRTIO_VSOCK_F_DGRAM           2       /* SOCK_DGRAM supported */
 
 struct virtio_vsock_config {
        uint64_t guest_cid;
-- 
2.20.1