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

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 21 Oct 2016 22:48:10 +0200
Paolo Bonzini <pbonzini@redhat.com> 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 <cornelia.huck@de.ibm.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  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.

(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