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Re: [PATCH v4 2/2] virtio-net: prevent offloads reset on migration
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [PATCH v4 2/2] virtio-net: prevent offloads reset on migration |
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Date: |
Fri, 11 Oct 2019 10:13:27 -0400 |
On Fri, Oct 11, 2019 at 03:58:04PM +0200, Mikhail Sennikovsky wrote:
> 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.
>
> Signed-off-by: Mikhail Sennikovsky <address@hidden>
kind of ugly, but works:
Reviewed-by: Michael S. Tsirkin <address@hidden>
Jason can you merge this and the previous patch pls?
> ---
> 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 b9e1cd7..6adb0fe 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 b96f0c6..07a9319 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;
> --
> 2.7.4