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Date:   Sun, 18 Oct 2020 06:25:55 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Tonghao Zhang <xiangxia.m.yue@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jason Wang <jasowang@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [virtio] 3618ad2a7c: kernel_BUG_at_drivers/net/virtio_net.c

On Sun, Oct 18, 2020 at 04:25:14PM +0800, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed the following commit (built with gcc-9):
> 
> commit: 3618ad2a7c0e78e4258386394d5d5f92a3dbccf8 ("virtio-net: ethtool configurable RXCSUM")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> 
> in testcase: trinity
> version: trinity-i386
> with following parameters:
> 
> 	runtime: 300s
> 
> test-description: Trinity is a linux system call fuzz tester.
> test-url: http://codemonkey.org.uk/projects/trinity/
> 
> 
> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G
> 
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> 
> 
> +----------------------------------------+------------+------------+
> |                                        | c9bf52a173 | 3618ad2a7c |
> +----------------------------------------+------------+------------+
> | boot_successes                         | 18         | 0          |
> | boot_failures                          | 0          | 20         |
> | kernel_BUG_at_drivers/net/virtio_net.c | 0          | 20         |
> | invalid_opcode:#[##]                   | 0          | 20         |
> | EIP:virtnet_send_command               | 0          | 20         |
> | Kernel_panic-not_syncing               | 0          | 20         |
> +----------------------------------------+------------+------------+
> 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <lkp@...el.com>
> 
> 
> [   72.229171] kernel BUG at drivers/net/virtio_net.c:1667!
> [   72.230266] invalid opcode: 0000 [#1] PREEMPT SMP
> [   72.231172] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc8-02934-g3618ad2a7c0e7 #1
> [   72.231172] EIP: virtnet_send_command+0x120/0x140
> [   72.231172] Code: 00 0f 94 c0 8b 7d f0 65 33 3d 14 00 00 00 75 1c 8d 65 f4 5b 5e 5f 5d c3 66 90 be 01 00 00 00 e9 6e ff ff ff 8d b6 00 00 00 00 <0f> 0b e8 d9 bb 82 00 eb 17 8d b4 26 00 00 00 00 8d b4 26 00 00 00
> [   72.231172] EAX: 0000000d EBX: f72895c0 ECX: 00000017 EDX: 00000011
> [   72.231172] ESI: f7197800 EDI: ed69bd00 EBP: ed69bcf4 ESP: ed69bc98
> [   72.231172] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
> [   72.231172] CR0: 80050033 CR2: 00000000 CR3: 02c84000 CR4: 000406f0
> [   72.231172] Call Trace:
> [   72.231172]  ? __virt_addr_valid+0x45/0x60
> [   72.231172]  ? ___cache_free+0x51f/0x760
> [   72.231172]  ? kobject_uevent_env+0xf4/0x560
> [   72.231172]  virtnet_set_guest_offloads+0x4d/0x80
> [   72.231172]  virtnet_set_features+0x85/0x120
> [   72.231172]  ? virtnet_set_guest_offloads+0x80/0x80
> [   72.231172]  __netdev_update_features+0x27a/0x8e0
> [   72.231172]  ? kobject_uevent+0xa/0x20
> [   72.231172]  ? netdev_register_kobject+0x12c/0x160
> [   72.231172]  register_netdevice+0x4fe/0x740
> [   72.231172]  register_netdev+0x1c/0x40
> [   72.231172]  virtnet_probe+0x728/0xb60
> [   72.231172]  ? _raw_spin_unlock+0x1d/0x40
> [   72.231172]  ? virtio_vdpa_get_status+0x1c/0x20
> [   72.231172]  virtio_dev_probe+0x1c6/0x271
> [   72.231172]  really_probe+0x195/0x2e0
> [   72.231172]  driver_probe_device+0x26/0x60
> [   72.231172]  device_driver_attach+0x49/0x60
> [   72.231172]  __driver_attach+0x46/0xc0
> [   72.231172]  ? device_driver_attach+0x60/0x60
> [   72.231172]  bus_for_each_dev+0x5d/0xa0
> [   72.231172]  driver_attach+0x19/0x20
> [   72.231172]  ? device_driver_attach+0x60/0x60
> [   72.231172]  bus_add_driver+0x197/0x1c0
> [   72.231172]  driver_register+0x66/0xc0
> [   72.231172]  register_virtio_driver+0x1b/0x40
> [   72.231172]  virtio_net_driver_init+0x61/0x86
> [   72.231172]  ? veth_init+0x14/0x14
> [   72.231172]  do_one_initcall+0x76/0x2e4
> [   72.231172]  ? rdinit_setup+0x2a/0x2a
> [   72.231172]  do_initcalls+0xb2/0xd5
> [   72.231172]  kernel_init_freeable+0x14f/0x179
> [   72.231172]  ? rest_init+0x100/0x100
> [   72.231172]  kernel_init+0xd/0xe0
> [   72.231172]  ret_from_fork+0x1c/0x30
> [   72.231172] Modules linked in:
> [   72.269563] ---[ end trace a6ebc4afea0e6cb1 ]---
> 
> 
> To reproduce:
> 
>         # build kernel
> 	cd linux
> 	cp config-5.9.0-rc8-02934-g3618ad2a7c0e7 .config
> 	make HOSTCC=gcc-9 CC=gcc-9 ARCH=i386 olddefconfig prepare modules_prepare bzImage
> 
>         git clone https://github.com/intel/lkp-tests.git
>         cd lkp-tests
>         bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email
> 
> 
> 
> Thanks,
> lkp
> 

OK I more or less see what is going on.

virtnet_set_features now calls virtnet_set_guest_offloads
unconditionally, it used to only call it when there is something
to configure.


If device does not have a control vq, everything breaks.

Looking at this some more, I noticed that it's not really checking the
hardware too much. E.g.

        if ((dev->features ^ features) & NETIF_F_LRO) {
                if (features & NETIF_F_LRO)
                        offloads |= GUEST_OFFLOAD_LRO_MASK &
                                    vi->guest_offloads_capable;
                else
                        offloads &= ~GUEST_OFFLOAD_LRO_MASK;
        }


and

#define GUEST_OFFLOAD_LRO_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
                                (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
                                (1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
                                (1ULL << VIRTIO_NET_F_GUEST_UFO))

But there's no guarantee that e.g. VIRTIO_NET_F_GUEST_TSO6 is set.
If it isn't command should not send it.

And also

static int virtnet_set_features(struct net_device *dev,
                                netdev_features_t features)
{
        struct virtnet_info *vi = netdev_priv(dev);
        u64 offloads = vi->guest_offloads;


seems wrong since guest_offloads is zero initialized,
it does not reflect the state after reset which comes from
the features.

I suggest we revert 3618ad2a7c0e78 for now.

Let's work on something more robust wrt possible hardware features.



-- 
MST

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