Re: [Qemu-devel] host stalls when qemu-system-aarch64 with kvm and pflash

[Radha Mohan]

On Wed, Mar 29, 2017 at 11:56 AM, Christoffer Dall <address@hidden> wrote:
> On Tue, Mar 28, 2017 at 01:24:15PM -0700, Radha Mohan wrote:
>> On Tue, Mar 28, 2017 at 1:16 PM, Christoffer Dall <address@hidden> wrote:
>> > Hi Radha,
>> >
>> > On Tue, Mar 28, 2017 at 12:58:24PM -0700, Radha Mohan wrote:
>> >> Hi,
>> >> I am seeing an issue with qemu-system-aarch64 when using pflash
>> >> (booting kernel via UEFI bios).
>> >>
>> >> Host kernel: 4.11.0-rc3-next-20170323
>> >> Qemu version: v2.9.0-rc1
>> >>
>> >> Command used:
>> >> ./aarch64-softmmu/qemu-system-aarch64 -cpu host -enable-kvm -M
>> >> virt,gic_version=3 -nographic -smp 1 -m 2048 -drive
>> >> if=none,id=hd0,file=/root/zesty-server-cloudimg-arm64.img,id=0 -device
>> >> virtio-blk-device,drive=hd0 -pflash /root/flash0.img -pflash
>> >> /root/flash1.img
>> >>
>> >>
>> >> As soon as the guest kernel boots the host starts to stall and prints
>> >> the below messages. And the system never recovers. I can neither
>> >> poweroff the guest nor the host. So I have resort to external power
>> >> reset of the host.
>> >>
>> >> ==================
>> >> [  116.199077] NMI watchdog: BUG: soft lockup - CPU#25 stuck for 23s!
>> >> [kworker/25:1:454]
>> >> [  116.206901] Modules linked in: binfmt_misc nls_iso8859_1 aes_ce_blk
>> >> shpchp crypto_simd gpio_keys cryptd aes_ce_cipher ghash_ce sha2_ce
>> >> sha1_ce uio_pdrv_genirq uio autofs4 btrfs raid10 rai
>> >> d456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor
>> >> raid6_pq libcrc32c raid1 raid0 multipath linear ast i2c_algo_bit ttm
>> >> drm_kms_helper syscopyarea sysfillrect sysimgblt fb_s
>> >> ys_fops drm nicvf ahci nicpf libahci thunder_bgx thunder_xcv
>> >> mdio_thunder mdio_cavium
>> >>
>> >> [  116.206995] CPU: 25 PID: 454 Comm: kworker/25:1 Not tainted
>> >> 4.11.0-rc3-next-20170323 #1
>> >> [  116.206997] Hardware name: www.cavium.com crb-1s/crb-1s, BIOS 0.3 Feb 
>> >> 23 2017
>> >> [  116.207010] Workqueue: events netstamp_clear
>> >> [  116.207015] task: ffff801f906b5400 task.stack: ffff801f901a4000
>> >> [  116.207020] PC is at smp_call_function_many+0x284/0x2e8
>> >> [  116.207023] LR is at smp_call_function_many+0x244/0x2e8
>> >> [  116.207026] pc : [<ffff000008156ecc>] lr : [<ffff000008156e8c>]
>> >> pstate: 80000145
>> >> [  116.207028] sp : ffff801f901a7be0
>> >> [  116.207030] x29: ffff801f901a7be0 x28: ffff000009139000
>> >> [  116.207036] x27: ffff000009139434 x26: 0000000000000080
>> >> [  116.207041] x25: 0000000000000000 x24: ffff0000081565d0
>> >> [  116.207047] x23: 0000000000000001 x22: ffff000008e11e00
>> >> [  116.207052] x21: ffff801f6d5cff00 x20: ffff801f6d5cff08
>> >> [  116.207057] x19: ffff000009138e38 x18: 0000000000000a03
>> >> [  116.207063] x17: 0000ffffb77c9028 x16: ffff0000082e81d8
>> >> [  116.207068] x15: 00003d0d6dd44d08 x14: 0036312196549b4a
>> >> [  116.207073] x13: 0000000058dabe4c x12: 0000000000000018
>> >> [  116.207079] x11: 00000000366e2f04 x10: 00000000000009f0
>> >> [  116.207084] x9 : ffff801f901a7d30 x8 : 0000000000000002
>> >> [  116.207089] x7 : 0000000000000000 x6 : 0000000000000000
>> >> [  116.207095] x5 : ffffffff00000000 x4 : 0000000000000020
>> >> [  116.207100] x3 : 0000000000000020 x2 : 0000000000000000
>> >> [  116.207105] x1 : ffff801f6d682578 x0 : 0000000000000003
>> >>
>> >> [  150.443116] INFO: rcu_sched self-detected stall on CPU
>> >> [  150.448261]  25-...: (14997 ticks this GP)
>> >> idle=47a/140000000000001/0 softirq=349/349 fqs=7495
>> >> [  150.451115] INFO: rcu_sched detected stalls on CPUs/tasks:
>> >> [  150.451123]  25-...: (14997 ticks this GP)
>> >> idle=47a/140000000000001/0 softirq=349/349 fqs=7495
>> >> [  150.451124]  (detected by 13, t=15002 jiffies, g=805, c=804, q=8384)
>> >> [  150.451136] Task dump for CPU 25:
>> >> [  150.451138] kworker/25:1    R  running task        0   454      2 
>> >> 0x00000002
>> >> [  150.451155] Workqueue: events netstamp_clear
>> >> [  150.451158] Call trace:
>> >> [  150.451164] [<ffff000008086188>] __switch_to+0x90/0xa8
>> >> [  150.451172] [<ffff0000081f6240>] static_key_slow_inc+0x128/0x138
>> >> [  150.451175] [<ffff0000081f6284>] static_key_enable+0x34/0x60
>> >> [  150.451178] [<ffff000008843268>] netstamp_clear+0x68/0x80
>> >> [  150.451181] [<ffff0000080e49a0>] process_one_work+0x158/0x478
>> >> [  150.451183] [<ffff0000080e4d10>] worker_thread+0x50/0x4a8
>> >> [  150.451187] [<ffff0000080ebd78>] kthread+0x108/0x138
>> >> [  150.451190] [<ffff0000080836c0>] ret_from_fork+0x10/0x50
>> >> [  150.477451]   (t=15008 jiffies g=805 c=804 q=8384)
>> >> [  150.482242] Task dump for CPU 25:
>> >> [  150.482245] kworker/25:1    R  running task        0   454      2 
>> >> 0x00000002
>> >> [  150.482259] Workqueue: events netstamp_clear
>> >> [  150.482264] Call trace:
>> >> [  150.482271] [<ffff00000808a530>] dump_backtrace+0x0/0x2b0
>> >> [  150.482277] [<ffff00000808a804>] show_stack+0x24/0x30
>> >> [  150.482281] [<ffff0000080fb750>] sched_show_task+0x128/0x178
>> >> [  150.482285] [<ffff0000080fd298>] dump_cpu_task+0x48/0x58
>> >> [  150.482288] [<ffff0000081f81e4>] rcu_dump_cpu_stacks+0xa0/0xe8
>> >> [  150.482297] [<ffff00000813983c>] rcu_check_callbacks+0x774/0x938
>> >> [  150.482305] [<ffff00000813fcb4>] update_process_times+0x34/0x60
>> >> [  150.482314] [<ffff000008151b80>] tick_sched_handle.isra.7+0x38/0x70
>> >> [  150.482319] [<ffff000008151c04>] tick_sched_timer+0x4c/0x98
>> >> [  150.482324] [<ffff000008140510>] __hrtimer_run_queues+0xd8/0x2b8
>> >> [  150.482328] [<ffff000008141180>] hrtimer_interrupt+0xa8/0x228
>> >> [  150.482334] [<ffff0000087f2a2c>] arch_timer_handler_phys+0x3c/0x50
>> >> [  150.482341] [<ffff00000812c194>] handle_percpu_devid_irq+0x8c/0x230
>> >> [  150.482344] [<ffff000008126174>] generic_handle_irq+0x34/0x50
>> >> [  150.482347] [<ffff000008126898>] __handle_domain_irq+0x68/0xc0
>> >> [  150.482351] [<ffff0000080817e4>] gic_handle_irq+0xc4/0x170
>> >> [  150.482356] Exception stack(0xffff801f901a7ab0 to 0xffff801f901a7be0)
>> >> [  150.482360] 7aa0:
>> >> 0000000000000003 ffff801f6d682578
>> >> [  150.482364] 7ac0: 0000000000000000 0000000000000020
>> >> 0000000000000020 ffffffff00000000
>> >> [  150.482367] 7ae0: 0000000000000000 0000000000000000
>> >> 0000000000000002 ffff801f901a7d30
>> >> [  150.482371] 7b00: 00000000000009f0 00000000366e2f04
>> >> 0000000000000018 0000000058dabe4c
>> >> [  150.482375] 7b20: 0036312196549b4a 00003d0d6dd44d08
>> >> ffff0000082e81d8 0000ffffb77c9028
>> >> [  150.482378] 7b40: 0000000000000a03 ffff000009138e38
>> >> ffff801f6d5cff08 ffff801f6d5cff00
>> >> [  150.482382] 7b60: ffff000008e11e00 0000000000000001
>> >> ffff0000081565d0 0000000000000000
>> >> [  150.482386] 7b80: 0000000000000080 ffff000009139434
>> >> ffff000009139000 ffff801f901a7be0
>> >> [  150.482390] 7ba0: ffff000008156e8c ffff801f901a7be0
>> >> ffff000008156ecc 0000000080000145
>> >> [  150.482394] 7bc0: ffff801f901a7be0 ffff000008156e68
>> >> ffffffffffffffff ffff000008156e8c
>> >> [  150.482397] [<ffff000008082ff4>] el1_irq+0xb4/0x140
>> >> [  150.482401] [<ffff000008156ecc>] smp_call_function_many+0x284/0x2e8
>> >> [  150.482405] [<ffff000008157020>] kick_all_cpus_sync+0x30/0x38
>> >> [  150.482409] [<ffff00000897c6cc>] aarch64_insn_patch_text+0xec/0xf8
>> >> [  150.482415] [<ffff000008095978>] arch_jump_label_transform+0x60/0x98
>> >> [  150.482420] [<ffff0000081f593c>] __jump_label_update+0x8c/0xa8
>> >> [  150.482423] [<ffff0000081f6088>] jump_label_update+0x58/0xe8
>> >> [  150.482429] [<ffff0000081f6240>] static_key_slow_inc+0x128/0x138
>> >> [  150.482434] [<ffff0000081f6284>] static_key_enable+0x34/0x60
>> >> [  150.482438] [<ffff000008843268>] netstamp_clear+0x68/0x80
>> >> [  150.482441] [<ffff0000080e49a0>] process_one_work+0x158/0x478
>> >> [  150.482444] [<ffff0000080e4d10>] worker_thread+0x50/0x4a8
>> >> [  150.482448] [<ffff0000080ebd78>] kthread+0x108/0x138
>> >> [  150.482451] [<ffff0000080836c0>] ret_from_fork+0x10/0x50
>> >>
>> >> ====================================
>> >>
>> >> I am observing that this usually happens when the guest tries to
>> >> bringup or use the default virtio-net interface.
>> >> And I am unable to reproduce this when directly booting the guest
>> >> kernel without UEFI BIOS.
>> >> So anyone observed similar issue ?
>> >>
>> >
>> > I haven't seen this myself.
>> >
>> > Have you tried with other versions of QEMU and the host kernel by any
>> > chance using the same setup?
>>
>> The earlier qemu version (atleast 2.5 which is default on ubuntu
>> 16.04) have different issue. The same thing happens when I use
>> vhost=on but without vhost and with virtio-net didn't see the issue.
>> The Armband folks have also reported the vhost issue here
>> https://bugs.launchpad.net/ubuntu/+source/edk2/+bug/1673564
>
> So I just ran your setup using the flash emulation on the ThunderX in
> packet.net and my host is happily continuing to run hackbench.

One more thing I see is the ubuntu cloud images run a cloud-init
service during boot and seems to do lot of network init, the bug
appears when doing such things.

>
>>
>> So I am beginning to think the issue could be related to the flash
>> emulation but wanted to check on ml if anyone else is seeing it. But
>> if it is flash emulation how can it hose the host like this ?
>
> Why do you think it's related to the flash emulation?

Because without pflash method and directly launching kernel using
"-kernel" option of qemu works ok.


>
> From what you're telling me it sounds much more like a vhost regression.
>
> Can you try with v4.10 of the kernel with vhost=on ?

Ok will try. I do think the issue could also be host kernel side and
something is triggering.
The newer qemu is having a default virtio-net interface. Does this use
vhost by default ?
And is there a way not to have a default virtio-net interface.

I am not specifying any vhost in my command.
My observation with vhost=on was with qemu-2.5 and 4.4 kernel from Ubuntu 16.04.

Another observation I have is, occasionally during the trials the
guest hangs at this point and host cpu goes into a softlockup after
sometime. I cannot kill the qemu either through qemu Ctrl-A+C+Q or
kill command from host.

------------- cut -----------------
EFI stub: Booting Linux Kernel...
EFI stub: EFI_RNG_PROTOCOL unavailable, no randomness supplied
EFI stub: Using DTB from configuration table
EFI stub: Exiting boot services and installing virtual address map...
[    0.000000] Booting Linux on physical CPU 0x0
------------- end ------------------


>
> Thanks,
> -Christoffer