Re: [Qemu-devel] [PATCH 07/13] virtio-scsi: always use dataplane path if ioeventfd is active

[Paolo Bonzini]

On 11/11/2016 05:09, Alex Williamson wrote:
> On Fri, 21 Oct 2016 22:48:10 +0200
> Paolo Bonzini <address@hidden> wrote:
> 
>> Override start_ioeventfd and stop_ioeventfd to start/stop the
>> whole dataplane logic.  This has some positive side effects:
>>
>> - no need anymore for virtio_add_queue_aio (i.e. a revert of
>>   commit 1c627137c10ee2dcf59e0383ade8a9abfa2d4355)
>>
>> - no need anymore to switch from generic ioeventfd handlers to
>>   dataplane
>>
>> It detects some errors better:
>>
>>     $ qemu-system-x86_64 -object iothread,id=io \
>>           -device virtio-scsi-pci,ioeventfd=off,iothread=io
>>     qemu-system-x86_64: -device virtio-scsi-pci,ioeventfd=off,iothread=io:
>>     ioeventfd is required for iothread
>>
>> while previously it would have started just fine.
>>
>> Reviewed-by: Cornelia Huck <address@hidden>
>> Signed-off-by: Paolo Bonzini <address@hidden>
>> ---
>>  hw/scsi/virtio-scsi-dataplane.c | 56 
>> +++++++++++++++++++++++++----------------
>>  hw/scsi/virtio-scsi.c           | 24 ++++++++----------
>>  include/hw/virtio/virtio-scsi.h |  6 ++---
>>  3 files changed, 48 insertions(+), 38 deletions(-)
> 
> Looks like this added a more subtle regression with MST's previous pull
> request, I have an OVMF/440FX/virtio-scsi/virtio-net/win8.1 VM, with
> this patch it fails to shutdown.  QEMU just spins at 400% load.

I cannot reproduce this one. :(  You said you get it even with vhost,
what if you remove VFIO and add a regular VGA?

If you can post a backtrace of all threads at the time of the hang, from
origin/master (so without vhost, and not at ad07cd6) that could help.

Paolo

> (ps from libvirt launched vm, linebreaks added)
> 
> /usr/local/bin/qemu-system-x86_64 -name guest=Steam,debug-threads=on -S \
>  -object 
> secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-54-Steam/master-key.aes
>  \
>  -machine pc-i440fx-2.8,accel=kvm,usb=off,vmport=off \
>  -cpu 
> host,hv_time,hv_relaxed,hv_vapic,hv_spinlocks=0x1fff,hv_vendor_id=KeenlyKVM,kvm=off
>  \
>  -drive 
> file=/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd,if=pflash,format=raw,unit=0,readonly=on
>  \
>  -drive 
> file=/var/lib/libvirt/qemu/nvram/Steam_VARS.fd,if=pflash,format=raw,unit=1 \
>  -m 4096 -mem-prealloc -mem-path /dev/hugepages/libvirt/qemu -realtime 
> mlock=off \
>  -smp 4,sockets=1,cores=4,threads=1 -uuid 
> 79f39860-d659-426b-89e8-90cb46ee57c6 \
>  -display none -no-user-config -nodefaults \
>  -chardev 
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-54-Steam/monitor.sock,server,nowait
>  \
>  -mon chardev=charmonitor,id=monitor,mode=control -rtc 
> base=localtime,driftfix=slew \
>  -global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -boot 
> menu=on,strict=on \
>  -device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x8.0x7 \
>  -device 
> ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x8
>  \
>  -device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x8.0x1 \
>  -device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x8.0x2 \
>  -device virtio-scsi-pci,id=scsi0,num_queues=4,bus=pci.0,addr=0x5 \
>  -drive 
> file=/mnt/store/vm/Steam.img,format=raw,if=none,id=drive-scsi0-0-0-0,cache=none
>  \
>  -device 
> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=2
>  \
>  -netdev tap,fd=28,id=hostnet0,vhost=on,vhostfd=30 \
>  -device 
> virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:60:ef:ac,bus=pci.0,addr=0x3
>  \
>  -device vfio-pci,host=01:00.0,id=hostdev0,bus=pci.0,addr=0x2 \
>  -device vfio-pci,host=01:00.1,id=hostdev1,bus=pci.0,addr=0x6,rombar=0 \
>  -device vfio-pci,host=02:00.0,id=hostdev2,bus=pci.0,addr=0x7 -snapshot -msg 
> timestamp=on
> 
> Fails:
> ad07cd6 virtio-scsi: always use dataplane path if ioeventfd is active
> 
> Works (but I'm not using virtio-blk):
> 9ffe337 virtio-blk: always use dataplane path if ioeventfd is active
> 
> Thanks,
> Alex
> 
>