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d="scan'208";a="86155238" From: Lin Liu To: CC: Lin Liu , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "moderated list:XEN HYPERVISOR INTERFACE" , "open list:NETWORKING DRIVERS" , open list Subject: [PATCH] drivers/net/netfront: Fix NULL sring after live migration Date: Tue, 29 Nov 2022 06:17:02 +0000 Message-ID: <20221129061702.60629-1-lin.liu@citrix.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1669702677122100001 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A NAPI is setup for each network sring to poll data to kernel The sring with source host is destroyed before live migration and new sring with target host is setup after live migration. The NAPI for the old sring is not deleted until setup new sring with target host after migration. With busy_poll/busy_read enabled, the NAPI can be polled before got deleted when resume VM. [50116.602938] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 [50116.603047] IP: xennet_poll+0xae/0xd20 [50116.603090] PGD 0 P4D 0 [50116.603118] Oops: 0000 [#1] SMP PTI [50116.604624] Call Trace: [50116.604674] ? finish_task_switch+0x71/0x230 [50116.604745] ? timerqueue_del+0x1d/0x40 [50116.604807] ? hrtimer_try_to_cancel+0xb5/0x110 [50116.604882] ? xennet_alloc_rx_buffers+0x2a0/0x2a0 [50116.604958] napi_busy_loop+0xdb/0x270 [50116.605017] sock_poll+0x87/0x90 [50116.605066] do_sys_poll+0x26f/0x580 [50116.605125] ? tracing_map_insert+0x1d4/0x2f0 [50116.605196] ? event_hist_trigger+0x14a/0x260 ... [50116.613598] ? finish_task_switch+0x71/0x230 [50116.614131] ? __schedule+0x256/0x890 [50116.614640] ? recalc_sigpending+0x1b/0x50 [50116.615144] ? xen_sched_clock+0x15/0x20 [50116.615643] ? __rb_reserve_next+0x12d/0x140 [50116.616138] ? ring_buffer_lock_reserve+0x123/0x3d0 [50116.616634] ? event_triggers_call+0x87/0xb0 [50116.617138] ? trace_event_buffer_commit+0x1c4/0x210 [50116.617625] ? xen_clocksource_get_cycles+0x15/0x20 [50116.618112] ? ktime_get_ts64+0x51/0xf0 [50116.618578] SyS_ppoll+0x160/0x1a0 [50116.619029] ? SyS_ppoll+0x160/0x1a0 [50116.619475] do_syscall_64+0x73/0x130 [50116.619901] entry_SYSCALL_64_after_hwframe+0x41/0xa6 ... [50116.806230] RIP: xennet_poll+0xae/0xd20 RSP: ffffb4f041933900 [50116.806772] CR2: 0000000000000008 [50116.807337] ---[ end trace f8601785b354351c ]--- xen frontend should remove the NAPIs for the old srings before live migration as the bond srings are destroyed There is a tiny window between the srings are set to NULL and the NAPIs are disabled, It is safe as the NAPI threads are still frozen at that time Signed-off-by: Lin Liu --- drivers/net/xen-netfront.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 9af2b027c19c..dc404e05970c 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1862,6 +1862,12 @@ static int netfront_resume(struct xenbus_device *dev) netif_tx_unlock_bh(info->netdev); =20 xennet_disconnect_backend(info); + + rtnl_lock(); + if (info->queues) + xennet_destroy_queues(info); + rtnl_unlock(); + return 0; } =20 --=20 2.17.1