[Qemu-devel] [PATCH for 2.4 V2] virtio: fix 1.0 virtqueue migration

[Jason Wang <jasowang@redhat.com>]

1.0 does not requires physically-contiguous pages layout for a
virtqueue. So we could not infer avail and used from desc. This means
we need to migrate vring.avail and vring.used when host support virtio
1.0. This fixes malfunction of virtio 1.0 device after migration.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
- Changes from V1: switch to use subsection to make debug easier
---
 hw/virtio/virtio.c         | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h |  6 +++++
 2 files changed, 62 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index ee4e07c..788b556 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1049,6 +1049,61 @@ static bool virtio_64bit_features_needed(void *opaque)
     return (vdev->host_features >> 32) != 0;
 }
 
+static bool virtio_virtqueue_needed(void *opaque)
+{
+    VirtIODevice *vdev = opaque;
+
+    return virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1);
+}
+
+static void put_virtqueue_state(QEMUFile *f, void *pv, size_t size)
+{
+    VirtIODevice *vdev = pv;
+    int i;
+
+    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+        qemu_put_be64(f, vdev->vq[i].vring.avail);
+        qemu_put_be64(f, vdev->vq[i].vring.used);
+    }
+}
+
+static int get_virtqueue_state(QEMUFile *f, void *pv, size_t size)
+{
+    VirtIODevice *vdev = pv;
+    int i;
+
+    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+        vdev->vq[i].vring.avail = qemu_get_be64(f);
+        vdev->vq[i].vring.used = qemu_get_be64(f);
+    }
+    return 0;
+}
+
+static VMStateInfo vmstate_info_virtqueue = {
+    .name = "virtqueue_state",
+    .get = get_virtqueue_state,
+    .put = put_virtqueue_state,
+};
+
+static const VMStateDescription vmstate_virtio_virtqueues = {
+    .name = "virtio/virtqueues",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = &virtio_virtqueue_needed,
+    .fields = (VMStateField[]) {
+        {
+            .name         = "virtqueues",
+            .version_id   = 0,
+            .field_exists = NULL,
+            .size         = 0,
+            .info         = &vmstate_info_virtqueue,
+            .flags        = VMS_SINGLE,
+            .offset       = 0,
+        },
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_virtio_device_endian = {
     .name = "virtio/device_endian",
     .version_id = 1,
@@ -1082,6 +1137,7 @@ static const VMStateDescription vmstate_virtio = {
     .subsections = (const VMStateDescription*[]) {
         &vmstate_virtio_device_endian,
         &vmstate_virtio_64bit_features,
+        &vmstate_virtio_virtqueues,
         NULL
     }
 };
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 59f0763..cccae89 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -272,6 +272,12 @@ static inline bool virtio_has_feature(VirtIODevice *vdev, unsigned int fbit)
     return __virtio_has_feature(vdev->guest_features, fbit);
 }
 
+static inline bool virtio_host_has_feature(VirtIODevice *vdev,
+                                           unsigned int fbit)
+{
+    return __virtio_has_feature(vdev->host_features, fbit);
+}
+
 static inline bool virtio_is_big_endian(VirtIODevice *vdev)
 {
     if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
-- 
2.1.4