Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Stefano Garzarella]

+Cc: qemu-devel@nongnu.org

Hi,

On Thu, Oct 01, 2020 at 01:26:51AM +0900, Ju Hyung Park wrote:
> Hi everyone.
> 
> I have recently switched to a setup running QEMU 5.0(which supports
> io_uring) for a Windows 10 guest on Linux v5.4.63.
> The QEMU hosts /dev/nvme0n1p3 to the guest with virtio-blk with
> discard/unmap enabled.

Please, can you share the qemu command line that you are using?
This can be useful for the analysis.

Thanks,
Stefano

> 
> I've been having a weird issue where the system would randomly hang
> whenever I turn on or shutdown the guest. The host will stay up for a
> bit and then just hang. No response on SSH, etc. Even ping doesn't
> work.
> 
> It's been hard to even get a log to debug the issue, but I've been
> able to get a show-backtrace-all-active-cpus sysrq dmesg on the most
> recent encounter with the issue and it's showing some io_uring
> functions.
> 
> Since I've been encountering the issue ever since I switched to QEMU
> 5.0, I suspect io_uring may be the culprit to the issue.
> 
> While I'd love to try out the mainline kernel, it's currently not
> feasible at the moment as I have to stay in linux-5.4.y. Backporting
> mainline's io_uring also seems to be a non-trivial job.
> 
> Any tips would be appreciated. I can build my own kernel and I'm
> willing to try out (backported) patches.
> 
> Thanks.
> 
> [243683.539303] NMI backtrace for cpu 1
> [243683.539303] CPU: 1 PID: 1527 Comm: qemu-system-x86 Tainted: P
>   W  O      5.4.63+ #1
> [243683.539303] Hardware name: System manufacturer System Product
> Name/PRIME Z370-A, BIOS 2401 07/12/2019
> [243683.539304] RIP: 0010:io_uring_flush+0x98/0x140
> [243683.539304] Code: e4 74 70 48 8b 93 e8 02 00 00 48 8b 32 48 8b 4a
> 08 48 89 4e 08 48 89 31 48 89 12 48 89 52 08 48 8b 72 f8 81 4a a8 00
> 40 00 00 <48> 85 f6 74 15 4c 3b 62 c8 75 0f ba 01 00 00 00 bf 02 00 00
> 00 e8
> [243683.539304] RSP: 0018:ffff8881f20c3e28 EFLAGS: 00000006
> [243683.539305] RAX: ffff888419cd94e0 RBX: ffff88842ba49800 RCX:
> ffff888419cd94e0
> [243683.539305] RDX: ffff888419cd94e0 RSI: ffff888419cd94d0 RDI:
> ffff88842ba49af8
> [243683.539306] RBP: ffff88842ba49af8 R08: 0000000000000001 R09:
> ffff88840d17aaf8
> [243683.539306] R10: 0000000000000001 R11: 00000000ffffffec R12:
> ffff88843c68c080
> [243683.539306] R13: ffff88842ba49ae8 R14: 0000000000000001 R15:
> 0000000000000000
> [243683.539307] FS:  0000000000000000(0000) GS:ffff88843ea80000(0000)
> knlGS:0000000000000000
> [243683.539307] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [243683.539307] CR2: 00007f3234b31f90 CR3: 0000000002608001 CR4:
> 00000000003726e0
> [243683.539307] Call Trace:
> [243683.539308]  ? filp_close+0x2a/0x60
> [243683.539308]  ? put_files_struct.part.0+0x57/0xb0
> [243683.539309]  ? do_exit+0x321/0xa70
> [243683.539309]  ? do_group_exit+0x35/0x90
> [243683.539309]  ? __x64_sys_exit_group+0xf/0x10
> [243683.539309]  ? do_syscall_64+0x41/0x160
> [243683.539309]  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [243684.753272] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [243684.753278] rcu: 1-...0: (1 GPs behind)
> idle=a5e/1/0x4000000000000000 softirq=7893711/7893712 fqs=2955
> [243684.753280] (detected by 3, t=6002 jiffies, g=17109677, q=117817)
> [243684.753282] Sending NMI from CPU 3 to CPUs 1:
> [243684.754285] NMI backtrace for cpu 1
> [243684.754285] CPU: 1 PID: 1527 Comm: qemu-system-x86 Tainted: P
>   W  O      5.4.63+ #1
> [243684.754286] Hardware name: System manufacturer System Product
> Name/PRIME Z370-A, BIOS 2401 07/12/2019
> [243684.754286] RIP: 0010:io_uring_flush+0x83/0x140
> [243684.754287] Code: 89 ef e8 00 36 92 00 48 8b 83 e8 02 00 00 49 39
> c5 74 52 4d 85 e4 74 70 48 8b 93 e8 02 00 00 48 8b 32 48 8b 4a 08 48
> 89 4e 08 <48> 89 31 48 89 12 48 89 52 08 48 8b 72 f8 81 4a a8 00 40 00
> 00 48
> [243684.754287] RSP: 0018:ffff8881f20c3e28 EFLAGS: 00000002
> [243684.754288] RAX: ffff888419cd94e0 RBX: ffff88842ba49800 RCX:
> ffff888419cd94e0
> [243684.754288] RDX: ffff888419cd94e0 RSI: ffff888419cd94e0 RDI:
> ffff88842ba49af8
> [243684.754289] RBP: ffff88842ba49af8 R08: 0000000000000001 R09:
> ffff88840d17aaf8
> [243684.754289] R10: 0000000000000001 R11: 00000000ffffffec R12:
> ffff88843c68c080
> [243684.754289] R13: ffff88842ba49ae8 R14: 0000000000000001 R15:
> 0000000000000000
> [243684.754290] FS:  0000000000000000(0000) GS:ffff88843ea80000(0000)
> knlGS:0000000000000000
> [243684.754290] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [243684.754291] CR2: 00007f3234b31f90 CR3: 0000000002608001 CR4:
> 00000000003726e0
> [243684.754291] Call Trace:
> [243684.754291]  ? filp_close+0x2a/0x60
> [243684.754291]  ? put_files_struct.part.0+0x57/0xb0
> [243684.754292]  ? do_exit+0x321/0xa70
> [243684.754292]  ? do_group_exit+0x35/0x90
> [243684.754292]  ? __x64_sys_exit_group+0xf/0x10
> [243684.754293]  ? do_syscall_64+0x41/0x160
> [243684.754293]  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Jack Wang]

Stefano Garzarella <sgarzare@redhat.com> 于2020年10月1日周四 上午10:59写道：
>
> +Cc: qemu-devel@nongnu.org
>
> Hi,
>
> On Thu, Oct 01, 2020 at 01:26:51AM +0900, Ju Hyung Park wrote:
> > Hi everyone.
> >
> > I have recently switched to a setup running QEMU 5.0(which supports
> > io_uring) for a Windows 10 guest on Linux v5.4.63.
> > The QEMU hosts /dev/nvme0n1p3 to the guest with virtio-blk with
> > discard/unmap enabled.
>
> Please, can you share the qemu command line that you are using?
> This can be useful for the analysis.
>
> Thanks,
> Stefano
>
> >
> > I've been having a weird issue where the system would randomly hang
> > whenever I turn on or shutdown the guest. The host will stay up for a
> > bit and then just hang. No response on SSH, etc. Even ping doesn't
> > work.
> >
> > It's been hard to even get a log to debug the issue, but I've been
> > able to get a show-backtrace-all-active-cpus sysrq dmesg on the most
> > recent encounter with the issue and it's showing some io_uring
> > functions.
> >
> > Since I've been encountering the issue ever since I switched to QEMU
> > 5.0, I suspect io_uring may be the culprit to the issue.
> >
> > While I'd love to try out the mainline kernel, it's currently not
> > feasible at the moment as I have to stay in linux-5.4.y. Backporting
> > mainline's io_uring also seems to be a non-trivial job.
> >
> > Any tips would be appreciated. I can build my own kernel and I'm
> > willing to try out (backported) patches.
> >
> > Thanks.
> >
> > [243683.539303] NMI backtrace for cpu 1
> > [243683.539303] CPU: 1 PID: 1527 Comm: qemu-system-x86 Tainted: P
> >   W  O      5.4.63+ #1
> > [243683.539303] Hardware name: System manufacturer System Product
> > Name/PRIME Z370-A, BIOS 2401 07/12/2019
> > [243683.539304] RIP: 0010:io_uring_flush+0x98/0x140
> > [243683.539304] Code: e4 74 70 48 8b 93 e8 02 00 00 48 8b 32 48 8b 4a
> > 08 48 89 4e 08 48 89 31 48 89 12 48 89 52 08 48 8b 72 f8 81 4a a8 00
> > 40 00 00 <48> 85 f6 74 15 4c 3b 62 c8 75 0f ba 01 00 00 00 bf 02 00 00
> > 00 e8
> > [243683.539304] RSP: 0018:ffff8881f20c3e28 EFLAGS: 00000006
> > [243683.539305] RAX: ffff888419cd94e0 RBX: ffff88842ba49800 RCX:
> > ffff888419cd94e0
> > [243683.539305] RDX: ffff888419cd94e0 RSI: ffff888419cd94d0 RDI:
> > ffff88842ba49af8
> > [243683.539306] RBP: ffff88842ba49af8 R08: 0000000000000001 R09:
> > ffff88840d17aaf8
> > [243683.539306] R10: 0000000000000001 R11: 00000000ffffffec R12:
> > ffff88843c68c080
> > [243683.539306] R13: ffff88842ba49ae8 R14: 0000000000000001 R15:
> > 0000000000000000
> > [243683.539307] FS:  0000000000000000(0000) GS:ffff88843ea80000(0000)
> > knlGS:0000000000000000
> > [243683.539307] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [243683.539307] CR2: 00007f3234b31f90 CR3: 0000000002608001 CR4:
> > 00000000003726e0
> > [243683.539307] Call Trace:
> > [243683.539308]  ? filp_close+0x2a/0x60
> > [243683.539308]  ? put_files_struct.part.0+0x57/0xb0
> > [243683.539309]  ? do_exit+0x321/0xa70
> > [243683.539309]  ? do_group_exit+0x35/0x90
> > [243683.539309]  ? __x64_sys_exit_group+0xf/0x10
> > [243683.539309]  ? do_syscall_64+0x41/0x160
> > [243683.539309]  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [243684.753272] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> > [243684.753278] rcu: 1-...0: (1 GPs behind)
> > idle=a5e/1/0x4000000000000000 softirq=7893711/7893712 fqs=2955
> > [243684.753280] (detected by 3, t=6002 jiffies, g=17109677, q=117817)
> > [243684.753282] Sending NMI from CPU 3 to CPUs 1:
> > [243684.754285] NMI backtrace for cpu 1
> > [243684.754285] CPU: 1 PID: 1527 Comm: qemu-system-x86 Tainted: P
> >   W  O      5.4.63+ #1
> > [243684.754286] Hardware name: System manufacturer System Product
> > Name/PRIME Z370-A, BIOS 2401 07/12/2019
> > [243684.754286] RIP: 0010:io_uring_flush+0x83/0x140
> > [243684.754287] Code: 89 ef e8 00 36 92 00 48 8b 83 e8 02 00 00 49 39
> > c5 74 52 4d 85 e4 74 70 48 8b 93 e8 02 00 00 48 8b 32 48 8b 4a 08 48
> > 89 4e 08 <48> 89 31 48 89 12 48 89 52 08 48 8b 72 f8 81 4a a8 00 40 00
> > 00 48
> > [243684.754287] RSP: 0018:ffff8881f20c3e28 EFLAGS: 00000002
> > [243684.754288] RAX: ffff888419cd94e0 RBX: ffff88842ba49800 RCX:
> > ffff888419cd94e0
> > [243684.754288] RDX: ffff888419cd94e0 RSI: ffff888419cd94e0 RDI:
> > ffff88842ba49af8
> > [243684.754289] RBP: ffff88842ba49af8 R08: 0000000000000001 R09:
> > ffff88840d17aaf8
> > [243684.754289] R10: 0000000000000001 R11: 00000000ffffffec R12:
> > ffff88843c68c080
> > [243684.754289] R13: ffff88842ba49ae8 R14: 0000000000000001 R15:
> > 0000000000000000
> > [243684.754290] FS:  0000000000000000(0000) GS:ffff88843ea80000(0000)
> > knlGS:0000000000000000
> > [243684.754290] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [243684.754291] CR2: 00007f3234b31f90 CR3: 0000000002608001 CR4:
> > 00000000003726e0
> > [243684.754291] Call Trace:
> > [243684.754291]  ? filp_close+0x2a/0x60
> > [243684.754291]  ? put_files_struct.part.0+0x57/0xb0
> > [243684.754292]  ? do_exit+0x321/0xa70
> > [243684.754292]  ? do_group_exit+0x35/0x90
> > [243684.754292]  ? __x64_sys_exit_group+0xf/0x10
> > [243684.754293]  ? do_syscall_64+0x41/0x160
> > [243684.754293]  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
>
>
I got something similar
[250145.410520] general protection fault: 0000 [#1] SMP

[250145.410868] CPU: 5 PID: 39269 Comm: qemu-5.0 Kdump: loaded
Tainted: G           O      5.4.61-pserver
#5.4.61-1+develop20200831.1341+7430880~deb10

[250145.411468] Hardware name: Supermicro Super Server/X11DDW-L, BIOS
3.3 02/21/2020

[250145.412051] RIP: 0010:io_cancel_async_work+0x48/0xa0

[250145.412386] Code: fb 48 8d bf f8 02 00 00 48 89 f5 e8 02 f1 69 00
48 8b 83 e8 02 00 00 49 39 c4 74 52 48 8b 83 e8 02 00 00 48 8b 08 48
8b 50 08 <48> 89 51 08 48 8

9 0a 48 8b 70 f8 48 89 00 48 89 40 08 81 48 a8 00

[250145.413239] RSP: 0018:ffffc2d34efb7cf8 EFLAGS: 00010083

[250145.413576] RAX: ffffec9879729a80 RBX: ffff9fa2740ac400 RCX:
06ffff8000000000

[250145.414153] RDX: ffff9fa2740ac6e8 RSI: ffffec9879729a40 RDI:
ffff9fa2740ac6f8

[250145.414729] RBP: ffff9fa1cf86c080 R08: ffff9fa199ccecf8 R09:
8000002f724b7067

[250145.415307] R10: ffffc2d34efb7b8c R11: 0000000000000003 R12:
ffff9fa2740ac6e8

[250145.415884] R13: 0000000000000000 R14: 000000000000000d R15:
ffff9fa1af48e068

[250145.416461] FS:  0000000000000000(0000) GS:ffff9fa280940000(0000)
knlGS:0000000000000000

[250145.417042] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033

[250145.417380] CR2: 00007f5f14188000 CR3: 0000002f0c408005 CR4:
00000000007626e0

[250145.417957] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000

[250145.418535] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400

[250145.419112] PKRU: 55555554

[250145.419438] Call Trace:

[250145.419768]  io_uring_flush+0x34/0x50

[250145.420101]  filp_close+0x31/0x60

[250145.420432]  put_files_struct+0x6c/0xc0

[250145.420767]  do_exit+0x347/0xa50

[250145.421097]  do_group_exit+0x3a/0x90

[250145.421429]  get_signal+0x125/0x7d0

[250145.421761]  do_signal+0x36/0x640

[250145.422090]  ? do_send_sig_info+0x5c/0x90

[250145.422423]  ? recalc_sigpending+0x17/0x50

[250145.422757]  exit_to_usermode_loop+0x61/0xd0

[250145.423090]  do_syscall_64+0xe6/0x120

[250145.423424]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

[250145.423761] RIP: 0033:0x7f5f176997bb

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Ju Hyung Park]

Hi Stefano,

On Thu, Oct 1, 2020 at 5:59 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
> Please, can you share the qemu command line that you are using?
> This can be useful for the analysis.

Sure.

QEMU:
/usr/bin/qemu-system-x86_64 -name guest=win10,debug-threads=on -S
-object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-1-win10/master-key.aes
-blockdev {"driver":"file","filename":"/usr/share/OVMF/OVMF_CODE.fd","node-name":"libvirt-pflash0-storage","auto-read-only":true,"discard":"unmap"}
-blockdev {"node-name":"libvirt-pflash0-format","read-only":true,"driver":"raw","file":"libvirt-pflash0-storage"}
-blockdev {"driver":"file","filename":"/var/lib/libvirt/qemu/nvram/win10_VARS.fd","node-name":"libvirt-pflash1-storage","auto-read-only":true,"discard":"unmap"}
-blockdev {"node-name":"libvirt-pflash1-format","read-only":false,"driver":"raw","file":"libvirt-pflash1-storage"}
-machine pc-q35-5.0,accel=kvm,usb=off,vmport=off,dump-guest-core=off,mem-merge=off,pflash0=libvirt-pflash0-format,pflash1=libvirt-pflash1-format
-cpu Skylake-Client-IBRS,ss=on,vmx=on,hypervisor=on,tsc-adjust=on,clflushopt=on,umip=on,md-clear=on,stibp=on,arch-capabilities=on,ssbd=on,xsaves=on,pdpe1gb=on,ibpb=on,amd-ssbd=on,fma=off,avx=off,f16c=off,rdrand=off,bmi1=off,hle=off,avx2=off,bmi2=off,rtm=off,rdseed=off,adx=off,hv-time,hv-relaxed,hv-vapic,hv-spinlocks=0x1fff,hv-vpindex,hv-runtime,hv-synic,hv-stimer,hv-reset
-m 8192 -mem-prealloc -mem-path /dev/hugepages/libvirt/qemu/1-win10
-overcommit mem-lock=off -smp 4,sockets=1,dies=1,cores=2,threads=2
-uuid 7ccc3031-1dab-4267-b72a-d60065b5ff7f -display none
-no-user-config -nodefaults -chardev
socket,id=charmonitor,fd=32,server,nowait -mon
chardev=charmonitor,id=monitor,mode=control -rtc
base=localtime,driftfix=slew -global kvm-pit.lost_tick_policy=delay
-no-hpet -no-shutdown -global ICH9-LPC.disable_s3=1 -global
ICH9-LPC.disable_s4=1 -boot menu=off,strict=on -device
pcie-root-port,port=0x8,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x1
-device pcie-root-port,port=0x9,chassis=2,id=pci.2,bus=pcie.0,addr=0x1.0x1
-device pcie-root-port,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x1.0x2
-device pcie-root-port,port=0xb,chassis=4,id=pci.4,bus=pcie.0,addr=0x1.0x3
-device pcie-pci-bridge,id=pci.5,bus=pci.2,addr=0x0 -device
qemu-xhci,id=usb,bus=pci.1,addr=0x0 -blockdev
{"driver":"host_device","filename":"/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":true},"auto-read-only":true,"discard":"unmap"}
-blockdev {"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","detect-zeroes":"unmap","cache":{"direct":false,"no-flush":true},"driver":"raw","file":"libvirt-1-storage"}
-device virtio-blk-pci,scsi=off,bus=pcie.0,addr=0xa,drive=libvirt-1-format,id=virtio-disk0,bootindex=1,write-cache=on
-netdev tap,fd=34,id=hostnet0 -device
e1000,netdev=hostnet0,id=net0,mac=52:54:00:c6:bb:bc,bus=pcie.0,addr=0x3
-device ich9-intel-hda,id=sound0,bus=pcie.0,addr=0x4 -device
hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device
vfio-pci,host=0000:00:02.0,id=hostdev0,bus=pcie.0,addr=0x2,rombar=0
-device virtio-balloon-pci,id=balloon0,bus=pcie.0,addr=0x8 -object
rng-random,id=objrng0,filename=/dev/urandom -device
virtio-rng-pci,rng=objrng0,id=rng0,bus=pcie.0,addr=0x9 -msg
timestamp=on

And I use libvirt 6.3.0 to manage the VM. Here's an xml of my VM.

<domain type="kvm">
  <name>win10</name>
  <uuid>7ccc3031-1dab-4267-b72a-d60065b5ff7f</uuid>
  <metadata>
    <libosinfo:libosinfo
xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/win/10"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit="KiB">8388608</memory>
  <currentMemory unit="KiB">8388608</currentMemory>
  <memoryBacking>
    <hugepages/>
    <nosharepages/>
  </memoryBacking>
  <vcpu placement="static">4</vcpu>
  <cputune>
    <vcpupin vcpu="0" cpuset="0"/>
    <vcpupin vcpu="1" cpuset="2"/>
    <vcpupin vcpu="2" cpuset="1"/>
    <vcpupin vcpu="3" cpuset="3"/>
  </cputune>
  <os>
    <type arch="x86_64" machine="pc-q35-5.0">hvm</type>
    <loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE.fd</loader>
    <nvram>/var/lib/libvirt/qemu/nvram/win10_VARS.fd</nvram>
    <boot dev="hd"/>
    <bootmenu enable="no"/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv>
      <relaxed state="on"/>
      <vapic state="on"/>
      <spinlocks state="on" retries="8191"/>
      <vpindex state="on"/>
      <runtime state="on"/>
      <synic state="on"/>
      <stimer state="on"/>
      <reset state="on"/>
    </hyperv>
    <vmport state="off"/>
  </features>
  <cpu mode="host-model" check="partial">
    <topology sockets="1" dies="1" cores="2" threads="2"/>
  </cpu>
  <clock offset="localtime">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
    <timer name="hypervclock" present="yes"/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled="no"/>
    <suspend-to-disk enabled="no"/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type="block" device="disk">
      <driver name="qemu" type="raw" cache="unsafe" discard="unmap"
detect_zeroes="unmap"/>
      <source dev="/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9"/>
      <target dev="vda" bus="virtio"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x0a"
function="0x0"/>
    </disk>
    <controller type="pci" index="0" model="pcie-root"/>
    <controller type="pci" index="1" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="1" port="0x8"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="2" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="2" port="0x9"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
function="0x1"/>
    </controller>
    <controller type="pci" index="3" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="3" port="0xa"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
function="0x2"/>
    </controller>
    <controller type="pci" index="4" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="4" port="0xb"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
function="0x3"/>
    </controller>
    <controller type="pci" index="5" model="pcie-to-pci-bridge">
      <model name="pcie-pci-bridge"/>
      <address type="pci" domain="0x0000" bus="0x02" slot="0x00"
function="0x0"/>
    </controller>
    <controller type="usb" index="0" model="qemu-xhci">
      <address type="pci" domain="0x0000" bus="0x01" slot="0x00"
function="0x0"/>
    </controller>
    <controller type="sata" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x1f"
function="0x2"/>
    </controller>
    <interface type="network">
      <mac address="52:54:00:c6:bb:bc"/>
      <source network="default"/>
      <model type="e1000"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03"
function="0x0"/>
    </interface>
    <input type="mouse" bus="ps2"/>
    <input type="keyboard" bus="ps2"/>
    <sound model="ich9">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x04"
function="0x0"/>
    </sound>
    <hostdev mode="subsystem" type="pci" managed="yes">
      <source>
        <address domain="0x0000" bus="0x00" slot="0x02" function="0x0"/>
      </source>
      <rom bar="off"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02"
function="0x0"/>
    </hostdev>
    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x08"
function="0x0"/>
    </memballoon>
    <rng model="virtio">
      <backend model="random">/dev/urandom</backend>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x09"
function="0x0"/>
    </rng>
  </devices>
</domain>

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Stefano Garzarella]

Hi Ju,

On Thu, Oct 01, 2020 at 11:30:14PM +0900, Ju Hyung Park wrote:
> Hi Stefano,
> 
> On Thu, Oct 1, 2020 at 5:59 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > Please, can you share the qemu command line that you are using?
> > This can be useful for the analysis.
> 
> Sure.

Thanks for sharing.

The issue seems related to io_uring and the new io_uring fd monitoring
implementation available from QEMU 5.0.

I'll try to reproduce.

For now, as a workaround, you can rebuild qemu by disabling io-uring support:

  ../configure --disable-linux-io-uring ...


Thanks,
Stefano

> 
> QEMU:
> /usr/bin/qemu-system-x86_64 -name guest=win10,debug-threads=on -S
> -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-1-win10/master-key.aes
> -blockdev {"driver":"file","filename":"/usr/share/OVMF/OVMF_CODE.fd","node-name":"libvirt-pflash0-storage","auto-read-only":true,"discard":"unmap"}
> -blockdev {"node-name":"libvirt-pflash0-format","read-only":true,"driver":"raw","file":"libvirt-pflash0-storage"}
> -blockdev {"driver":"file","filename":"/var/lib/libvirt/qemu/nvram/win10_VARS.fd","node-name":"libvirt-pflash1-storage","auto-read-only":true,"discard":"unmap"}
> -blockdev {"node-name":"libvirt-pflash1-format","read-only":false,"driver":"raw","file":"libvirt-pflash1-storage"}
> -machine pc-q35-5.0,accel=kvm,usb=off,vmport=off,dump-guest-core=off,mem-merge=off,pflash0=libvirt-pflash0-format,pflash1=libvirt-pflash1-format
> -cpu Skylake-Client-IBRS,ss=on,vmx=on,hypervisor=on,tsc-adjust=on,clflushopt=on,umip=on,md-clear=on,stibp=on,arch-capabilities=on,ssbd=on,xsaves=on,pdpe1gb=on,ibpb=on,amd-ssbd=on,fma=off,avx=off,f16c=off,rdrand=off,bmi1=off,hle=off,avx2=off,bmi2=off,rtm=off,rdseed=off,adx=off,hv-time,hv-relaxed,hv-vapic,hv-spinlocks=0x1fff,hv-vpindex,hv-runtime,hv-synic,hv-stimer,hv-reset
> -m 8192 -mem-prealloc -mem-path /dev/hugepages/libvirt/qemu/1-win10
> -overcommit mem-lock=off -smp 4,sockets=1,dies=1,cores=2,threads=2
> -uuid 7ccc3031-1dab-4267-b72a-d60065b5ff7f -display none
> -no-user-config -nodefaults -chardev
> socket,id=charmonitor,fd=32,server,nowait -mon
> chardev=charmonitor,id=monitor,mode=control -rtc
> base=localtime,driftfix=slew -global kvm-pit.lost_tick_policy=delay
> -no-hpet -no-shutdown -global ICH9-LPC.disable_s3=1 -global
> ICH9-LPC.disable_s4=1 -boot menu=off,strict=on -device
> pcie-root-port,port=0x8,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x1
> -device pcie-root-port,port=0x9,chassis=2,id=pci.2,bus=pcie.0,addr=0x1.0x1
> -device pcie-root-port,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x1.0x2
> -device pcie-root-port,port=0xb,chassis=4,id=pci.4,bus=pcie.0,addr=0x1.0x3
> -device pcie-pci-bridge,id=pci.5,bus=pci.2,addr=0x0 -device
> qemu-xhci,id=usb,bus=pci.1,addr=0x0 -blockdev
> {"driver":"host_device","filename":"/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":true},"auto-read-only":true,"discard":"unmap"}
> -blockdev {"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","detect-zeroes":"unmap","cache":{"direct":false,"no-flush":true},"driver":"raw","file":"libvirt-1-storage"}
> -device virtio-blk-pci,scsi=off,bus=pcie.0,addr=0xa,drive=libvirt-1-format,id=virtio-disk0,bootindex=1,write-cache=on
> -netdev tap,fd=34,id=hostnet0 -device
> e1000,netdev=hostnet0,id=net0,mac=52:54:00:c6:bb:bc,bus=pcie.0,addr=0x3
> -device ich9-intel-hda,id=sound0,bus=pcie.0,addr=0x4 -device
> hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device
> vfio-pci,host=0000:00:02.0,id=hostdev0,bus=pcie.0,addr=0x2,rombar=0
> -device virtio-balloon-pci,id=balloon0,bus=pcie.0,addr=0x8 -object
> rng-random,id=objrng0,filename=/dev/urandom -device
> virtio-rng-pci,rng=objrng0,id=rng0,bus=pcie.0,addr=0x9 -msg
> timestamp=on
> 
> And I use libvirt 6.3.0 to manage the VM. Here's an xml of my VM.
> 
> <domain type="kvm">
>   <name>win10</name>
>   <uuid>7ccc3031-1dab-4267-b72a-d60065b5ff7f</uuid>
>   <metadata>
>     <libosinfo:libosinfo
> xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
>       <libosinfo:os id="http://microsoft.com/win/10"/>
>     </libosinfo:libosinfo>
>   </metadata>
>   <memory unit="KiB">8388608</memory>
>   <currentMemory unit="KiB">8388608</currentMemory>
>   <memoryBacking>
>     <hugepages/>
>     <nosharepages/>
>   </memoryBacking>
>   <vcpu placement="static">4</vcpu>
>   <cputune>
>     <vcpupin vcpu="0" cpuset="0"/>
>     <vcpupin vcpu="1" cpuset="2"/>
>     <vcpupin vcpu="2" cpuset="1"/>
>     <vcpupin vcpu="3" cpuset="3"/>
>   </cputune>
>   <os>
>     <type arch="x86_64" machine="pc-q35-5.0">hvm</type>
>     <loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE.fd</loader>
>     <nvram>/var/lib/libvirt/qemu/nvram/win10_VARS.fd</nvram>
>     <boot dev="hd"/>
>     <bootmenu enable="no"/>
>   </os>
>   <features>
>     <acpi/>
>     <apic/>
>     <hyperv>
>       <relaxed state="on"/>
>       <vapic state="on"/>
>       <spinlocks state="on" retries="8191"/>
>       <vpindex state="on"/>
>       <runtime state="on"/>
>       <synic state="on"/>
>       <stimer state="on"/>
>       <reset state="on"/>
>     </hyperv>
>     <vmport state="off"/>
>   </features>
>   <cpu mode="host-model" check="partial">
>     <topology sockets="1" dies="1" cores="2" threads="2"/>
>   </cpu>
>   <clock offset="localtime">
>     <timer name="rtc" tickpolicy="catchup"/>
>     <timer name="pit" tickpolicy="delay"/>
>     <timer name="hpet" present="no"/>
>     <timer name="hypervclock" present="yes"/>
>   </clock>
>   <on_poweroff>destroy</on_poweroff>
>   <on_reboot>restart</on_reboot>
>   <on_crash>destroy</on_crash>
>   <pm>
>     <suspend-to-mem enabled="no"/>
>     <suspend-to-disk enabled="no"/>
>   </pm>
>   <devices>
>     <emulator>/usr/bin/qemu-system-x86_64</emulator>
>     <disk type="block" device="disk">
>       <driver name="qemu" type="raw" cache="unsafe" discard="unmap"
> detect_zeroes="unmap"/>
>       <source dev="/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9"/>
>       <target dev="vda" bus="virtio"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x0a"
> function="0x0"/>
>     </disk>
>     <controller type="pci" index="0" model="pcie-root"/>
>     <controller type="pci" index="1" model="pcie-root-port">
>       <model name="pcie-root-port"/>
>       <target chassis="1" port="0x8"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> function="0x0" multifunction="on"/>
>     </controller>
>     <controller type="pci" index="2" model="pcie-root-port">
>       <model name="pcie-root-port"/>
>       <target chassis="2" port="0x9"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> function="0x1"/>
>     </controller>
>     <controller type="pci" index="3" model="pcie-root-port">
>       <model name="pcie-root-port"/>
>       <target chassis="3" port="0xa"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> function="0x2"/>
>     </controller>
>     <controller type="pci" index="4" model="pcie-root-port">
>       <model name="pcie-root-port"/>
>       <target chassis="4" port="0xb"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> function="0x3"/>
>     </controller>
>     <controller type="pci" index="5" model="pcie-to-pci-bridge">
>       <model name="pcie-pci-bridge"/>
>       <address type="pci" domain="0x0000" bus="0x02" slot="0x00"
> function="0x0"/>
>     </controller>
>     <controller type="usb" index="0" model="qemu-xhci">
>       <address type="pci" domain="0x0000" bus="0x01" slot="0x00"
> function="0x0"/>
>     </controller>
>     <controller type="sata" index="0">
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x1f"
> function="0x2"/>
>     </controller>
>     <interface type="network">
>       <mac address="52:54:00:c6:bb:bc"/>
>       <source network="default"/>
>       <model type="e1000"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x03"
> function="0x0"/>
>     </interface>
>     <input type="mouse" bus="ps2"/>
>     <input type="keyboard" bus="ps2"/>
>     <sound model="ich9">
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x04"
> function="0x0"/>
>     </sound>
>     <hostdev mode="subsystem" type="pci" managed="yes">
>       <source>
>         <address domain="0x0000" bus="0x00" slot="0x02" function="0x0"/>
>       </source>
>       <rom bar="off"/>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x02"
> function="0x0"/>
>     </hostdev>
>     <memballoon model="virtio">
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x08"
> function="0x0"/>
>     </memballoon>
>     <rng model="virtio">
>       <backend model="random">/dev/urandom</backend>
>       <address type="pci" domain="0x0000" bus="0x00" slot="0x09"
> function="0x0"/>
>     </rng>
>   </devices>
> </domain>
> 

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Ju Hyung Park]

A small update:

As per Stefano's suggestion, disabling io_uring support from QEMU from
the configuration step did fix the problem and I'm no longer having
hangs.

Looks like it __is__ an io_uring issue :(

Btw, I used liburing fe50048 for linking QEMU.

Thanks.


On Fri, Oct 2, 2020 at 4:35 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> Hi Ju,
>
> On Thu, Oct 01, 2020 at 11:30:14PM +0900, Ju Hyung Park wrote:
> > Hi Stefano,
> >
> > On Thu, Oct 1, 2020 at 5:59 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > Please, can you share the qemu command line that you are using?
> > > This can be useful for the analysis.
> >
> > Sure.
>
> Thanks for sharing.
>
> The issue seems related to io_uring and the new io_uring fd monitoring
> implementation available from QEMU 5.0.
>
> I'll try to reproduce.
>
> For now, as a workaround, you can rebuild qemu by disabling io-uring support:
>
>   ../configure --disable-linux-io-uring ...
>
>
> Thanks,
> Stefano
>
> >
> > QEMU:
> > /usr/bin/qemu-system-x86_64 -name guest=win10,debug-threads=on -S
> > -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-1-win10/master-key.aes
> > -blockdev {"driver":"file","filename":"/usr/share/OVMF/OVMF_CODE.fd","node-name":"libvirt-pflash0-storage","auto-read-only":true,"discard":"unmap"}
> > -blockdev {"node-name":"libvirt-pflash0-format","read-only":true,"driver":"raw","file":"libvirt-pflash0-storage"}
> > -blockdev {"driver":"file","filename":"/var/lib/libvirt/qemu/nvram/win10_VARS.fd","node-name":"libvirt-pflash1-storage","auto-read-only":true,"discard":"unmap"}
> > -blockdev {"node-name":"libvirt-pflash1-format","read-only":false,"driver":"raw","file":"libvirt-pflash1-storage"}
> > -machine pc-q35-5.0,accel=kvm,usb=off,vmport=off,dump-guest-core=off,mem-merge=off,pflash0=libvirt-pflash0-format,pflash1=libvirt-pflash1-format
> > -cpu Skylake-Client-IBRS,ss=on,vmx=on,hypervisor=on,tsc-adjust=on,clflushopt=on,umip=on,md-clear=on,stibp=on,arch-capabilities=on,ssbd=on,xsaves=on,pdpe1gb=on,ibpb=on,amd-ssbd=on,fma=off,avx=off,f16c=off,rdrand=off,bmi1=off,hle=off,avx2=off,bmi2=off,rtm=off,rdseed=off,adx=off,hv-time,hv-relaxed,hv-vapic,hv-spinlocks=0x1fff,hv-vpindex,hv-runtime,hv-synic,hv-stimer,hv-reset
> > -m 8192 -mem-prealloc -mem-path /dev/hugepages/libvirt/qemu/1-win10
> > -overcommit mem-lock=off -smp 4,sockets=1,dies=1,cores=2,threads=2
> > -uuid 7ccc3031-1dab-4267-b72a-d60065b5ff7f -display none
> > -no-user-config -nodefaults -chardev
> > socket,id=charmonitor,fd=32,server,nowait -mon
> > chardev=charmonitor,id=monitor,mode=control -rtc
> > base=localtime,driftfix=slew -global kvm-pit.lost_tick_policy=delay
> > -no-hpet -no-shutdown -global ICH9-LPC.disable_s3=1 -global
> > ICH9-LPC.disable_s4=1 -boot menu=off,strict=on -device
> > pcie-root-port,port=0x8,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x1
> > -device pcie-root-port,port=0x9,chassis=2,id=pci.2,bus=pcie.0,addr=0x1.0x1
> > -device pcie-root-port,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x1.0x2
> > -device pcie-root-port,port=0xb,chassis=4,id=pci.4,bus=pcie.0,addr=0x1.0x3
> > -device pcie-pci-bridge,id=pci.5,bus=pci.2,addr=0x0 -device
> > qemu-xhci,id=usb,bus=pci.1,addr=0x0 -blockdev
> > {"driver":"host_device","filename":"/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":true},"auto-read-only":true,"discard":"unmap"}
> > -blockdev {"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","detect-zeroes":"unmap","cache":{"direct":false,"no-flush":true},"driver":"raw","file":"libvirt-1-storage"}
> > -device virtio-blk-pci,scsi=off,bus=pcie.0,addr=0xa,drive=libvirt-1-format,id=virtio-disk0,bootindex=1,write-cache=on
> > -netdev tap,fd=34,id=hostnet0 -device
> > e1000,netdev=hostnet0,id=net0,mac=52:54:00:c6:bb:bc,bus=pcie.0,addr=0x3
> > -device ich9-intel-hda,id=sound0,bus=pcie.0,addr=0x4 -device
> > hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device
> > vfio-pci,host=0000:00:02.0,id=hostdev0,bus=pcie.0,addr=0x2,rombar=0
> > -device virtio-balloon-pci,id=balloon0,bus=pcie.0,addr=0x8 -object
> > rng-random,id=objrng0,filename=/dev/urandom -device
> > virtio-rng-pci,rng=objrng0,id=rng0,bus=pcie.0,addr=0x9 -msg
> > timestamp=on
> >
> > And I use libvirt 6.3.0 to manage the VM. Here's an xml of my VM.
> >
> > <domain type="kvm">
> >   <name>win10</name>
> >   <uuid>7ccc3031-1dab-4267-b72a-d60065b5ff7f</uuid>
> >   <metadata>
> >     <libosinfo:libosinfo
> > xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
> >       <libosinfo:os id="http://microsoft.com/win/10"/>
> >     </libosinfo:libosinfo>
> >   </metadata>
> >   <memory unit="KiB">8388608</memory>
> >   <currentMemory unit="KiB">8388608</currentMemory>
> >   <memoryBacking>
> >     <hugepages/>
> >     <nosharepages/>
> >   </memoryBacking>
> >   <vcpu placement="static">4</vcpu>
> >   <cputune>
> >     <vcpupin vcpu="0" cpuset="0"/>
> >     <vcpupin vcpu="1" cpuset="2"/>
> >     <vcpupin vcpu="2" cpuset="1"/>
> >     <vcpupin vcpu="3" cpuset="3"/>
> >   </cputune>
> >   <os>
> >     <type arch="x86_64" machine="pc-q35-5.0">hvm</type>
> >     <loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE.fd</loader>
> >     <nvram>/var/lib/libvirt/qemu/nvram/win10_VARS.fd</nvram>
> >     <boot dev="hd"/>
> >     <bootmenu enable="no"/>
> >   </os>
> >   <features>
> >     <acpi/>
> >     <apic/>
> >     <hyperv>
> >       <relaxed state="on"/>
> >       <vapic state="on"/>
> >       <spinlocks state="on" retries="8191"/>
> >       <vpindex state="on"/>
> >       <runtime state="on"/>
> >       <synic state="on"/>
> >       <stimer state="on"/>
> >       <reset state="on"/>
> >     </hyperv>
> >     <vmport state="off"/>
> >   </features>
> >   <cpu mode="host-model" check="partial">
> >     <topology sockets="1" dies="1" cores="2" threads="2"/>
> >   </cpu>
> >   <clock offset="localtime">
> >     <timer name="rtc" tickpolicy="catchup"/>
> >     <timer name="pit" tickpolicy="delay"/>
> >     <timer name="hpet" present="no"/>
> >     <timer name="hypervclock" present="yes"/>
> >   </clock>
> >   <on_poweroff>destroy</on_poweroff>
> >   <on_reboot>restart</on_reboot>
> >   <on_crash>destroy</on_crash>
> >   <pm>
> >     <suspend-to-mem enabled="no"/>
> >     <suspend-to-disk enabled="no"/>
> >   </pm>
> >   <devices>
> >     <emulator>/usr/bin/qemu-system-x86_64</emulator>
> >     <disk type="block" device="disk">
> >       <driver name="qemu" type="raw" cache="unsafe" discard="unmap"
> > detect_zeroes="unmap"/>
> >       <source dev="/dev/disk/by-partuuid/05c3750b-060f-4703-95ea-6f5e546bf6e9"/>
> >       <target dev="vda" bus="virtio"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x0a"
> > function="0x0"/>
> >     </disk>
> >     <controller type="pci" index="0" model="pcie-root"/>
> >     <controller type="pci" index="1" model="pcie-root-port">
> >       <model name="pcie-root-port"/>
> >       <target chassis="1" port="0x8"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> > function="0x0" multifunction="on"/>
> >     </controller>
> >     <controller type="pci" index="2" model="pcie-root-port">
> >       <model name="pcie-root-port"/>
> >       <target chassis="2" port="0x9"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> > function="0x1"/>
> >     </controller>
> >     <controller type="pci" index="3" model="pcie-root-port">
> >       <model name="pcie-root-port"/>
> >       <target chassis="3" port="0xa"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> > function="0x2"/>
> >     </controller>
> >     <controller type="pci" index="4" model="pcie-root-port">
> >       <model name="pcie-root-port"/>
> >       <target chassis="4" port="0xb"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x01"
> > function="0x3"/>
> >     </controller>
> >     <controller type="pci" index="5" model="pcie-to-pci-bridge">
> >       <model name="pcie-pci-bridge"/>
> >       <address type="pci" domain="0x0000" bus="0x02" slot="0x00"
> > function="0x0"/>
> >     </controller>
> >     <controller type="usb" index="0" model="qemu-xhci">
> >       <address type="pci" domain="0x0000" bus="0x01" slot="0x00"
> > function="0x0"/>
> >     </controller>
> >     <controller type="sata" index="0">
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x1f"
> > function="0x2"/>
> >     </controller>
> >     <interface type="network">
> >       <mac address="52:54:00:c6:bb:bc"/>
> >       <source network="default"/>
> >       <model type="e1000"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x03"
> > function="0x0"/>
> >     </interface>
> >     <input type="mouse" bus="ps2"/>
> >     <input type="keyboard" bus="ps2"/>
> >     <sound model="ich9">
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x04"
> > function="0x0"/>
> >     </sound>
> >     <hostdev mode="subsystem" type="pci" managed="yes">
> >       <source>
> >         <address domain="0x0000" bus="0x00" slot="0x02" function="0x0"/>
> >       </source>
> >       <rom bar="off"/>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x02"
> > function="0x0"/>
> >     </hostdev>
> >     <memballoon model="virtio">
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x08"
> > function="0x0"/>
> >     </memballoon>
> >     <rng model="virtio">
> >       <backend model="random">/dev/urandom</backend>
> >       <address type="pci" domain="0x0000" bus="0x00" slot="0x09"
> > function="0x0"/>
> >     </rng>
> >   </devices>
> > </domain>
> >
>

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Jens Axboe]

On 10/16/20 12:04 PM, Ju Hyung Park wrote:
> A small update:
> 
> As per Stefano's suggestion, disabling io_uring support from QEMU from
> the configuration step did fix the problem and I'm no longer having
> hangs.
> 
> Looks like it __is__ an io_uring issue :(

Would be great if you could try 5.4.71 and see if that helps for your
issue.

-- 
Jens Axboe

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Ju Hyung Park]

Hi Jens.

On Sat, Oct 17, 2020 at 3:07 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> Would be great if you could try 5.4.71 and see if that helps for your
> issue.
>

Oh wow, yeah it did fix the issue.

I'm able to reliably turn off and start the VM multiple times in a row.
Double checked by confirming QEMU is dynamically linked to liburing.so.1.

Looks like those 4 io_uring fixes helped.

Thanks!

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Jens Axboe]

On 10/17/20 8:29 AM, Ju Hyung Park wrote:
> Hi Jens.
> 
> On Sat, Oct 17, 2020 at 3:07 AM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> Would be great if you could try 5.4.71 and see if that helps for your
>> issue.
>>
> 
> Oh wow, yeah it did fix the issue.
> 
> I'm able to reliably turn off and start the VM multiple times in a row.
> Double checked by confirming QEMU is dynamically linked to liburing.so.1.
> 
> Looks like those 4 io_uring fixes helped.

Awesome, thanks for testing!

-- 
Jens Axboe

Re: io_uring possibly the culprit for qemu hang (linux-5.4.y)

[Pankaj Gupta]

@Jack Wang,
Maybe four io_uring patches in 5.4.71 fixes the issue for you as well?

Thanks,
Pankaj

> Hi Jens.
>
> On Sat, Oct 17, 2020 at 3:07 AM Jens Axboe <axboe@kernel.dk> wrote:
> >
> > Would be great if you could try 5.4.71 and see if that helps for your
> > issue.
> >
>
> Oh wow, yeah it did fix the issue.
>
> I'm able to reliably turn off and start the VM multiple times in a row.
> Double checked by confirming QEMU is dynamically linked to liburing.so.1.
>
> Looks like those 4 io_uring fixes helped.
>
> Thanks!
>