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    Subject[PATCH 5.14 082/849] xen/netfront: stop tx queues during live migration
    Date
    From: Dongli Zhang <dongli.zhang@oracle.com>

    [ Upstream commit 042b2046d0f05cf8124c26ff65dbb6148a4404fb ]

    The tx queues are not stopped during the live migration. As a result, the
    ndo_start_xmit() may access netfront_info->queues which is freed by
    talk_to_netback()->xennet_destroy_queues().

    This patch is to netif_device_detach() at the beginning of xen-netfront
    resuming, and netif_device_attach() at the end of resuming.

    CPU A CPU B

    talk_to_netback()
    -> if (info->queues)
    xennet_destroy_queues(info);
    to free netfront_info->queues

    xennet_start_xmit()
    to access netfront_info->queues

    -> err = xennet_create_queues(info, &num_queues);

    The idea is borrowed from virtio-net.

    Cc: Joe Jin <joe.jin@oracle.com>
    Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/xen-netfront.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
    index 44275908d61a2..0169f7743b6d3 100644
    --- a/drivers/net/xen-netfront.c
    +++ b/drivers/net/xen-netfront.c
    @@ -1669,6 +1669,10 @@ static int netfront_resume(struct xenbus_device *dev)

    dev_dbg(&dev->dev, "%s\n", dev->nodename);

    + netif_tx_lock_bh(info->netdev);
    + netif_device_detach(info->netdev);
    + netif_tx_unlock_bh(info->netdev);
    +
    xennet_disconnect_backend(info);
    return 0;
    }
    @@ -2283,6 +2287,10 @@ static int xennet_connect(struct net_device *dev)
    * domain a kick because we've probably just requeued some
    * packets.
    */
    + netif_tx_lock_bh(np->netdev);
    + netif_device_attach(np->netdev);
    + netif_tx_unlock_bh(np->netdev);
    +
    netif_carrier_on(np->netdev);
    for (j = 0; j < num_queues; ++j) {
    queue = &np->queues[j];
    --
    2.33.0


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