On 09/20/2010 11:47 AM, Michael S. Tsirkin wrote:
On Mon, Sep 20, 2010 at 11:41:45AM -0500, Anthony Liguori wrote:
On 09/20/2010 11:30 AM, Michael S. Tsirkin wrote:
With -netdev, virtio devices present offload
features to guest, depending on the backend used.
Thus, removing host ntedev peer while guest is
active leads to guest-visible inconsistency and/or crashes.
See e.g. https://bugzilla.redhat.com/show_bug.cgi?id=623735
As a solution, while guest (NIC) peer device exists,
we must prevent the host peer from being deleted.
This patch does this by adding peer_deleted flag in nic state:
if host device is going away while guest device
is around, set this flag and keep host device around
for as long as guest device exists.
Having an unclear life cycle really worries me.
Wouldn't the more correct solution be to avoid removing the netdev
device until after the peer has successfully been removed?
Regards,
Anthony Liguori
This is exactly what the patch does.
At the management layer instead of doing it magically in the backend.
IOW, if device_del returns and the device isn't actually deleted, that's
a bug and addressing it like this just means we'll trip over it
somewhere else.
We'll have the same problem with drive_del.
Regards,
Anthony Liguori
Signed-off-by: Michael S. Tsirkin<m...@redhat.com>
---
net.c | 21 ++++++++++++++++++++-
net.h | 1 +
2 files changed, 21 insertions(+), 1 deletions(-)
diff --git a/net.c b/net.c
index 3d0fde7..10855d1 100644
--- a/net.c
+++ b/net.c
@@ -286,12 +286,31 @@ void qemu_del_vlan_client(VLANClientState *vc)
if (vc->vlan) {
QTAILQ_REMOVE(&vc->vlan->clients, vc, next);
} else {
+ /* Even if client will not be deleted yet, remove it from list so it
+ * does not appear in monitor. */
+ QTAILQ_REMOVE(&non_vlan_clients, vc, next);
+ /* Detect that guest-visible (NIC) peer is active, and delay deletion.
+ * */
+ if (vc->peer&& vc->peer->info->type == NET_CLIENT_TYPE_NIC) {
+ NICState *nic = DO_UPCAST(NICState, nc, vc->peer);
+ assert(!nic->peer_deleted);
+ nic->peer_deleted = true;
+ return;
+ }
if (vc->send_queue) {
qemu_del_net_queue(vc->send_queue);
}
- QTAILQ_REMOVE(&non_vlan_clients, vc, next);
if (vc->peer) {
vc->peer->peer = NULL;
+ /* If this is a guest-visible (NIC) device,
+ * and peer has already been removed from monitor,
+ * delete it here. */
+ if (vc->info->type == NET_CLIENT_TYPE_NIC) {
+ NICState *nic = DO_UPCAST(NICState, nc, vc);
+ if (nic->peer_deleted) {
+ qemu_del_vlan_client(vc->peer);
+ }
+ }
}
}
diff --git a/net.h b/net.h
index 518cf9c..44c31a9 100644
--- a/net.h
+++ b/net.h
@@ -72,6 +72,7 @@ typedef struct NICState {
VLANClientState nc;
NICConf *conf;
void *opaque;
+ bool peer_deleted;
} NICState;
struct VLANState {
