Iterative live migration for virtio-net sends an initial
VMStateDescription while the source is still active. Because data
continues to flow for virtio-net, the guest's avail index continues to
increment after last_avail_idx had already been sent. This causes the
destination to often see something like this from virtio_error():
VQ 0 size 0x100 Guest index 0x0 inconsistent with Host index 0xc: delta 0xfff4
This patch suppresses this consistency check if we're loading the
initial VMStateDescriptions via iterative migration and unsuppresses
it for the stop-and-copy phase when the final VMStateDescriptions
(carrying the correct indices) are loaded.
A temporary VirtIODevMigration migration data structure is introduced here to
represent the iterative migration process for a VirtIODevice. For now it
just holds a flag to indicate whether or not the initial
VMStateDescription was sent during the iterative live migration process.
Signed-off-by: Jonah Palmer <jonah.pal...@oracle.com>
---
hw/net/virtio-net.c | 13 +++++++++++++
hw/virtio/virtio.c | 32 ++++++++++++++++++++++++--------
include/hw/virtio/virtio.h | 6 ++++++
3 files changed, 43 insertions(+), 8 deletions(-)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 86a6fe5b91..b7ac5e8278 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3843,12 +3843,19 @@ static void virtio_net_save_cleanup(void *opaque)
static int virtio_net_load_setup(QEMUFile *f, void *opaque, Error **errp)
{
+ VirtIONet *n = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(n);
+ vdev->migration = g_new0(VirtIODevMigration, 1);
+ vdev->migration->iterative_vmstate_loaded = false;
+
return 0;
}
static int virtio_net_load_state(QEMUFile *f, void *opaque, int version_id)
{
VirtIONet *n = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(n);
+ VirtIODevMigration *mig = vdev->migration;
uint64_t flag;
flag = qemu_get_be64(f);
@@ -3861,6 +3868,7 @@ static int virtio_net_load_state(QEMUFile *f, void
*opaque, int version_id)
case VNET_MIG_F_INIT_STATE:
{
vmstate_load_state(f, &vmstate_virtio_net, n,
VIRTIO_NET_VM_VERSION);
+ mig->iterative_vmstate_loaded = true;
break;
}
default:
@@ -3875,6 +3883,11 @@ static int virtio_net_load_state(QEMUFile *f, void
*opaque, int version_id)
static int virtio_net_load_cleanup(void *opaque)
{
+ VirtIONet *n = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(n);
+ g_free(vdev->migration);
+ vdev->migration = NULL;
+
return 0;
}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 5534251e01..68957ee7d1 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3222,6 +3222,7 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int
version_id)
int32_t config_len;
uint32_t num;
uint32_t features;
+ bool inconsistent_indices;
BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
@@ -3365,6 +3366,16 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int
version_id)
if (vdev->vq[i].vring.desc) {
uint16_t nheads;
+ /*
+ * Ring indices will be inconsistent during iterative migration.
The actual
+ * indices will be sent later during the stop-and-copy phase.
+ */
+ if (vdev->migration) {
+ inconsistent_indices =
!vdev->migration->iterative_vmstate_loaded;
+ } else {
+ inconsistent_indices = false;
+ }
+
/*
* VIRTIO-1 devices migrate desc, used, and avail ring addresses so
* only the region cache needs to be set up. Legacy devices need
@@ -3384,14 +3395,19 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int
version_id)
continue;
}
- nheads = vring_avail_idx(&vdev->vq[i]) -
vdev->vq[i].last_avail_idx;
- /* Check it isn't doing strange things with descriptor numbers. */
- if (nheads > vdev->vq[i].vring.num) {
- virtio_error(vdev, "VQ %d size 0x%x Guest index 0x%x "
- "inconsistent with Host index 0x%x: delta 0x%x",
- i, vdev->vq[i].vring.num,
- vring_avail_idx(&vdev->vq[i]),
- vdev->vq[i].last_avail_idx, nheads);
+ if (!inconsistent_indices) {
+ nheads = vring_avail_idx(&vdev->vq[i]) -
vdev->vq[i].last_avail_idx;
+ /* Check it isn't doing strange things with descriptor
numbers. */
+ if (nheads > vdev->vq[i].vring.num) {
+ virtio_error(vdev, "VQ %d size 0x%x Guest index 0x%x "
+ "inconsistent with Host index 0x%x: delta
0x%x",
+ i, vdev->vq[i].vring.num,
+ vring_avail_idx(&vdev->vq[i]),
+ vdev->vq[i].last_avail_idx, nheads);
+ inconsistent_indices = true;
+ }
+ }
+ if (inconsistent_indices) {
vdev->vq[i].used_idx = 0;
vdev->vq[i].shadow_avail_idx = 0;
vdev->vq[i].inuse = 0;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 214d4a77e9..06b6e6ba65 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -98,6 +98,11 @@ enum virtio_device_endian {
VIRTIO_DEVICE_ENDIAN_BIG,
};
+/* VirtIODevice iterative live migration data structure */
+typedef struct VirtIODevMigration {
+ bool iterative_vmstate_loaded;
+} VirtIODevMigration;
+
/**
* struct VirtIODevice - common VirtIO structure
* @name: name of the device
@@ -151,6 +156,7 @@ struct VirtIODevice
bool disable_legacy_check;
bool vhost_started;
VMChangeStateEntry *vmstate;
+ VirtIODevMigration *migration;
char *bus_name;
uint8_t device_endian;
/**
--
2.47.1
