Re: [Qemu-devel] [PATCH V2 00/20] Multiqueue virtio-net

[Jason Wang]

On 01/29/2013 01:36 PM, Wanlong Gao wrote:
> On 01/28/2013 12:24 PM, Jason Wang wrote:
>> On 01/28/2013 11:27 AM, Wanlong Gao wrote:
>>> On 01/25/2013 06:35 PM, Jason Wang wrote:
>>>> Hello all:
>>>>
>>>> This seires is an update of last version of multiqueue virtio-net support.
>>>>
>>>> This series tries to brings multiqueue support to virtio-net through a
>>>> multiqueue support tap backend and multiple vhost threads.
>>>>
>>>> To support this, multiqueue nic support were added to qemu. This is done by
>>>> introducing an array of NetClientStates in NICState, and make each pair of 
>>>> peers
>>>> to be an queue of the nic. This is done in patch 1-7.
>>>>
>>>> Tap were also converted to be able to create a multiple queue
>>>> backend. Currently, only linux support this by issuing TUNSETIFF N times 
>>>> with
>>>> the same device name to create N queues. Each fd returned by TUNSETIFF 
>>>> were a
>>>> queue supported by kernel. Three new command lines were introduced, 
>>>> "queues"
>>>> were used to tell how many queues will be created by qemu; "fds" were used 
>>>> to
>>>> pass multiple pre-created tap file descriptors to qemu; "vhostfds" were 
>>>> used to
>>>> pass multiple pre-created vhost descriptors to qemu. This is done in patch 
>>>> 8-13.
>>>>
>>>> A method of deleting a queue and queue_index were also introduce for 
>>>> virtio,
>>>> this is done in patch 14-15.
>>>>
>>>> Vhost were also changed to support multiqueue by introducing a start vq 
>>>> index
>>>> which tracks the first virtqueue that will be used by vhost instead of the
>>>> assumption that the vhost always use virtqueue from index 0. This is done 
>>>> in
>>>> patch 16.
>>>>
>>>> The last part is the multiqueue userspace changes, this is done in patch 
>>>> 17-20.
>>>>
>>>> With this changes, user could start a multiqueue virtio-net device through
>>>>
>>>> ./qemu -netdev tap,id=hn0,queues=2,vhost=on -device 
>>>> virtio-net-pci,netdev=hn0
>>>>
>>>> Management tools such as libvirt can pass multiple pre-created 
>>>> fds/vhostfds through
>>>>
>>>> ./qemu -netdev tap,id=hn0,fds=X:Y,vhostfds=M:N -device 
>>>> virtio-net-pci,netdev=hn0
>>>>
>>>> No git tree this round since github is unavailable in China...
>>> I saw that github had already been opened again. I can use it.
>> Thanks for reminding, I've pushed the new bits to
>> git://github.com/jasowang/qemu.git.
> I got host kernel oops here using your qemu tree and 3.8-rc5 kernel on host,
>
> [31499.754779] BUG: unable to handle kernel NULL pointer dereference at       
>     (null)
> [31499.757098] IP: [<ffffffff816475ef>] _raw_spin_lock_irqsave+0x1f/0x40
> [31499.758304] PGD 0 
> [31499.759498] Oops: 0002 [#1] SMP 
> [31499.760704] Modules linked in: tcp_lp fuse xt_CHECKSUM lockd 
> ipt_MASQUERADE sunrpc bnep bluetooth rfkill bridge stp llc iptable_nat 
> nf_nat_ipv4 nf_nat iptable_mangle nf_conntr
> ack_ipv4 nf_defrag_ipv4 nf_conntrack snd_hda_codec_realtek snd_hda_intel 
> snd_hda_codec vhost_net tun snd_hwdep macvtap snd_seq macvlan coretemp 
> kvm_intel snd_seq_device kvm snd_p
> cm crc32c_intel r8169 snd_page_alloc snd_timer ghash_clmulni_intel snd mei 
> iTCO_wdt mii microcode iTCO_vendor_support uinput serio_raw wmi i2c_i801 
> lpc_ich soundcore pcspkr mfd_c
> ore i915 video i2c_algo_bit drm_kms_helper drm i2c_core [last unloaded: 
> ip6t_REJECT]
> [31499.766412] CPU 2 
> [31499.766426] Pid: 18742, comm: vhost-18728 Not tainted 3.8.0-rc5 #1 LENOVO 
> QiTianM4300/To be filled by O.E.M.
> [31499.769340] RIP: 0010:[<ffffffff816475ef>]  [<ffffffff816475ef>] 
> _raw_spin_lock_irqsave+0x1f/0x40
> [31499.770861] RSP: 0018:ffff8801b2f9dd08  EFLAGS: 00010086
> [31499.772380] RAX: 0000000000000286 RBX: 0000000000000000 RCX: 
> 0000000000000000
> [31499.773916] RDX: 0000000000000100 RSI: 0000000000000286 RDI: 
> 0000000000000000
> [31499.775394] RBP: ffff8801b2f9dd08 R08: ffff880132ed4368 R09: 
> 0000000000000000
> [31499.776923] R10: 0000000000000001 R11: 0000000000000001 R12: 
> ffff880132ed8590
> [31499.778466] R13: ffff880232a6c290 R14: ffff880132ed42b0 R15: 
> ffff880132ed0078
> [31499.780012] FS:  0000000000000000(0000) GS:ffff88023fb00000(0000) 
> knlGS:0000000000000000
> [31499.781574] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [31499.783126] CR2: 0000000000000000 CR3: 0000000132d9c000 CR4: 
> 00000000000427e0
> [31499.784696] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [31499.786267] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 
> 0000000000000400
> [31499.787822] Process vhost-18728 (pid: 18742, threadinfo ffff8801b2f9c000, 
> task ffff880036959740)
> [31499.788821] Stack:
> [31499.790392]  ffff8801b2f9dd38 ffffffff81082534 0000000000000000 
> 0000000000000001
> [31499.792029]  ffff880132ed0000 ffff880232a6c290 ffff8801b2f9dd48 
> ffffffffa023fab6
> [31499.793677]  ffff8801b2f9de28 ffffffffa0242f64 ffff8801b2f9ddb8 
> ffffffff8109e0e0
> [31499.795332] Call Trace:
> [31499.796974]  [<ffffffff81082534>] remove_wait_queue+0x24/0x50
> [31499.798641]  [<ffffffffa023fab6>] vhost_poll_stop+0x16/0x20 [vhost_net]
> [31499.800313]  [<ffffffffa0242f64>] handle_tx+0x4c4/0x680 [vhost_net]
> [31499.801995]  [<ffffffff8109e0e0>] ? idle_balance+0x1b0/0x2f0
> [31499.803685]  [<ffffffffa0243155>] handle_tx_kick+0x15/0x20 [vhost_net]
> [31499.805128]  [<ffffffffa023f95d>] vhost_worker+0xed/0x190 [vhost_net]
> [31499.806842]  [<ffffffffa023f870>] ? vhost_work_flush+0x110/0x110 
> [vhost_net]
> [31499.808553]  [<ffffffff81081b70>] kthread+0xc0/0xd0
> [31499.810259]  [<ffffffff81010000>] ? 
> ftrace_define_fields_xen_mc_entry+0x30/0xf0
> [31499.811996]  [<ffffffff81081ab0>] ? kthread_create_on_node+0x120/0x120
> [31499.813726]  [<ffffffff8164fb2c>] ret_from_fork+0x7c/0xb0
> [31499.815442]  [<ffffffff81081ab0>] ? kthread_create_on_node+0x120/0x120
> [31499.817168] Code: 08 61 cb ff 48 89 d0 5d c3 0f 1f 00 66 66 66 66 90 55 48 
> 89 e5 9c 58 66 66 90 66 90 48 89 c6 fa 66 66 90 66 66 90 ba 00 01 00 00 <f0> 
> 66 0f c1 17 0f b6 ce 38 d1 74 0e 0f 1f 44 00 00 f3 90 0f b6 
> [31499.821098] RIP  [<ffffffff816475ef>] _raw_spin_lock_irqsave+0x1f/0x40
> [31499.823040]  RSP <ffff8801b2f9dd08>
> [31499.824976] CR2: 0000000000000000
> [31499.844842] ---[ end trace b7130aab34f0ed9c ]---
>
>
> According printing the value, I saw that the NULL pointer is poll->wqh in 
> vhost_poll_stop(),
>
> [  136.616527] vhost_net: poll = ffff8802081f8578
> [  136.616529] vhost_net: poll>wqh =           (null)
> [  136.616530] vhost_net: &poll->wait = ffff8802081f8590
> [  136.622478] Modules linked in: fuse ebtable_nat xt_CHECKSUM lockd sunrpc 
> ipt_MASQUERADE nf_conntrack_netbios_ns bnep nf_conntrack_broadcast bluetooth 
> bridge rfkill ip6table_mangle stp llc ip6t_REJECT nf_conntrack_ipv6 
> nf_defrag_ipv6 iptable_nat nf_nat_ipv4 nf_nat iptable_mangle 
> nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ebtable_filter 
> ebtables ip6table_filter ip6_tables snd_hda_codec_realtek snd_hda_intel 
> vhost_net snd_hda_codec tun macvtap snd_hwdep macvlan snd_seq snd_seq_device 
> coretemp snd_pcm kvm_intel kvm snd_page_alloc crc32c_intel snd_timer 
> ghash_clmulni_intel snd r8169 iTCO_wdt microcode iTCO_vendor_support mei 
> lpc_ich pcspkr mii soundcore mfd_core i2c_i801 serio_raw wmi uinput i915 
> video i2c_algo_bit drm_kms_helper drm i2c_core
> [  136.663172]  [<ffffffffa0283afc>] vhost_poll_stop+0x5c/0x70 [vhost_net]
> [  136.664880]  [<ffffffffa0286cf2>] handle_tx+0x262/0x650 [vhost_net]
> [  136.668289]  [<ffffffffa0287115>] handle_tx_kick+0x15/0x20 [vhost_net]
> [  136.670013]  [<ffffffffa028395d>] vhost_worker+0xed/0x190 [vhost_net]
> [  136.671737]  [<ffffffffa0283870>] ? vhost_work_flush+0x110/0x110 
> [vhost_net]
>
>
> But I don't know whether we should check poll->wqh here. Or it's a qemu bug 
> causes host kernel oops?

Right, it's a bug of vhost which should check poll->wqh and POLLERR.

I've posted the fixes in netdev:
http://marc.info/?l=linux-netdev&m=135937170929355&w=2

You can try the fixes there. It should fix your panic.

Thanks
>
> Thanks,
> Wanlong Gao
>
>>> Thanks,
>>> Wanlong Gao
>>>
>>>
>>