[qemu-xen stable-4.13] virtio-net: prevent offloads reset on migration

[patchbot@xxxxxxx]

commit 4887acf574a573137660aa98d9d422ece0a41a5a
Author:     Mikhail Sennikovsky <mikhail.sennikovskii@xxxxxxxxxxxxxxx>
AuthorDate: Fri Oct 11 15:58:04 2019 +0200
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Nov 4 08:24:34 2019 -0600

    virtio-net: prevent offloads reset on migration
    
    Currently offloads disabled by guest via the 
VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET
    command are not preserved on VM migration.
    Instead all offloads reported by guest features (via 
VIRTIO_PCI_GUEST_FEATURES)
    get enabled.
    What happens is: first the VirtIONet::curr_guest_offloads gets restored and 
offloads
    are getting set correctly:
    
     #0  qemu_set_offload (nc=0x555556a11400, csum=1, tso4=0, tso6=0, ecn=0, 
ufo=0) at net/net.c:474
     #1  virtio_net_apply_guest_offloads (n=0x555557701ca0) at 
hw/net/virtio-net.c:720
     #2  virtio_net_post_load_device (opaque=0x555557701ca0, version_id=11) at 
hw/net/virtio-net.c:2334
     #3  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577c80 
<vmstate_virtio_net_device>, opaque=0x555557701ca0, version_id=11)
         at migration/vmstate.c:168
     #4  virtio_load (vdev=0x555557701ca0, f=0x5555569dc010, version_id=11) at 
hw/virtio/virtio.c:2197
     #5  virtio_device_get (f=0x5555569dc010, opaque=0x555557701ca0, size=0, 
field=0x55555668cd00 <__compound_literal.5>) at hw/virtio/virtio.c:2036
     #6  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577ce0 
<vmstate_virtio_net>, opaque=0x555557701ca0, version_id=11) at 
migration/vmstate.c:143
     #7  vmstate_load (f=0x5555569dc010, se=0x5555578189e0) at 
migration/savevm.c:829
     #8  qemu_loadvm_section_start_full (f=0x5555569dc010, mis=0x5555569eee20) 
at migration/savevm.c:2211
     #9  qemu_loadvm_state_main (f=0x5555569dc010, mis=0x5555569eee20) at 
migration/savevm.c:2395
     #10 qemu_loadvm_state (f=0x5555569dc010) at migration/savevm.c:2467
     #11 process_incoming_migration_co (opaque=0x0) at migration/migration.c:449
    
    However later on the features are getting restored, and offloads get reset 
to
    everything supported by features:
    
     #0  qemu_set_offload (nc=0x555556a11400, csum=1, tso4=1, tso6=1, ecn=0, 
ufo=0) at net/net.c:474
     #1  virtio_net_apply_guest_offloads (n=0x555557701ca0) at 
hw/net/virtio-net.c:720
     #2  virtio_net_set_features (vdev=0x555557701ca0, features=5104441767) at 
hw/net/virtio-net.c:773
     #3  virtio_set_features_nocheck (vdev=0x555557701ca0, val=5104441767) at 
hw/virtio/virtio.c:2052
     #4  virtio_load (vdev=0x555557701ca0, f=0x5555569dc010, version_id=11) at 
hw/virtio/virtio.c:2220
     #5  virtio_device_get (f=0x5555569dc010, opaque=0x555557701ca0, size=0, 
field=0x55555668cd00 <__compound_literal.5>) at hw/virtio/virtio.c:2036
     #6  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577ce0 
<vmstate_virtio_net>, opaque=0x555557701ca0, version_id=11) at 
migration/vmstate.c:143
     #7  vmstate_load (f=0x5555569dc010, se=0x5555578189e0) at 
migration/savevm.c:829
     #8  qemu_loadvm_section_start_full (f=0x5555569dc010, mis=0x5555569eee20) 
at migration/savevm.c:2211
     #9  qemu_loadvm_state_main (f=0x5555569dc010, mis=0x5555569eee20) at 
migration/savevm.c:2395
     #10 qemu_loadvm_state (f=0x5555569dc010) at migration/savevm.c:2467
     #11 process_incoming_migration_co (opaque=0x0) at migration/migration.c:449
    
    Fix this by preserving the state in saved_guest_offloads field and
    pushing out offload initialization to the new post load hook.
    
    Cc: qemu-stable@xxxxxxxxxx
    Signed-off-by: Mikhail Sennikovsky <mikhail.sennikovskii@xxxxxxxxxxxxxxx>
    Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
    (cherry picked from commit 7788c3f2e21e35902d45809b236791383bbb613e)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 hw/net/virtio-net.c            | 27 ++++++++++++++++++++++++---
 include/hw/virtio/virtio-net.h |  2 ++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index b9e1cd71cf..6adb0fe252 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -2330,9 +2330,13 @@ static int virtio_net_post_load_device(void *opaque, int 
version_id)
         n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
     }
 
-    if (peer_has_vnet_hdr(n)) {
-        virtio_net_apply_guest_offloads(n);
-    }
+    /*
+     * curr_guest_offloads will be later overwritten by the
+     * virtio_set_features_nocheck call done from the virtio_load.
+     * Here we make sure it is preserved and restored accordingly
+     * in the virtio_net_post_load_virtio callback.
+     */
+    n->saved_guest_offloads = n->curr_guest_offloads;
 
     virtio_net_set_queues(n);
 
@@ -2367,6 +2371,22 @@ static int virtio_net_post_load_device(void *opaque, int 
version_id)
     return 0;
 }
 
+static int virtio_net_post_load_virtio(VirtIODevice *vdev)
+{
+    VirtIONet *n = VIRTIO_NET(vdev);
+    /*
+     * The actual needed state is now in saved_guest_offloads,
+     * see virtio_net_post_load_device for detail.
+     * Restore it back and apply the desired offloads.
+     */
+    n->curr_guest_offloads = n->saved_guest_offloads;
+    if (peer_has_vnet_hdr(n)) {
+        virtio_net_apply_guest_offloads(n);
+    }
+
+    return 0;
+}
+
 /* tx_waiting field of a VirtIONetQueue */
 static const VMStateDescription vmstate_virtio_net_queue_tx_waiting = {
     .name = "virtio-net-queue-tx_waiting",
@@ -2909,6 +2929,7 @@ static void virtio_net_class_init(ObjectClass *klass, 
void *data)
     vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
     vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;
     vdc->legacy_features |= (0x1 << VIRTIO_NET_F_GSO);
+    vdc->post_load = virtio_net_post_load_virtio;
     vdc->vmsd = &vmstate_virtio_net_device;
 }
 
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index b96f0c643f..07a9319f4b 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -182,6 +182,8 @@ struct VirtIONet {
     char *netclient_name;
     char *netclient_type;
     uint64_t curr_guest_offloads;
+    /* used on saved state restore phase to preserve the curr_guest_offloads */
+    uint64_t saved_guest_offloads;
     AnnounceTimer announce_timer;
     bool needs_vnet_hdr_swap;
     bool mtu_bypass_backend;
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.13