Re: [Qemu-devel] vhost-net issue: does not survive reboot on ppc64

[Zhi Yong Wu]

On Sat, Dec 21, 2013 at 11:01 PM, Alexey Kardashevskiy <address@hidden> wrote:
> Hi!
HI, Alexey

>
> I am having a problem with virtio-net + vhost on POWER7 machine - it does
> not survive reboot of the guest.
Can you let me login to your environment for debug? I am interested in
trying to fix this issue.

>
> Steps to reproduce:
> 1. boot the guest
> 2. configure eth0 and do ping - everything works
> 3. reboot the guest (i.e. type "reboot")
> 4. when it is booted, eth0 can be configured but will not work at all.
>
> The test is:
> ifconfig eth0 172.20.1.2 up
> ping 172.20.1.23
>
> If to run tcpdump on the host's "tap-id3" interface, it shows no trafic
> coming from the guest. If to compare how it works before and after reboot,
> I can see the guest doing an ARP request for 172.20.1.23 and receives the
> response and it does the same after reboot but the answer does not come.
>
> If to remove vhost=on, it is all good. If to try Fedora19
> (v3.10-something), it all good again - works before and after reboot.
>
>
> And there 2 questions:
>
> 1. does anybody have any clue what might go wrong after reboot?
>
> 2. Is there any good material to read about what exactly and how vhost
> accelerates?
>
> My understanding is that packets from the guest to the real network are
> going as:
> 1. guest's virtio-pci-net does ioport(VIRTIO_PCI_QUEUE_NOTIFY)
> 2. QEMU's net/virtio-net.c calls qemu_net_queue_deliver()
> 3. QEMU's net/tap.c calls tap_write_packet() and this is how the host knows
> that there is a new packet.
>
>
> Thanks!
>
>
> This how I run QEMU:
> ./qemu-system-ppc64 \
> -enable-kvm \
> -m 2048 \
> -machine pseries \
> -initrd 1.cpio \
> -kernel vml312_virtio_net_dbg \
> -nographic \
> -vga none \
> -netdev
> tap,id=id3,ifname=tap-id3,script=ifup.sh,downscript=ifdown.sh,vhost=on \
> -device virtio-net-pci,id=id4,netdev=id3,mac=C0:41:49:4b:00:00
>
>
> That is bridge config:
> address@hidden ~]$ brctl show
> bridge name     bridge id               STP enabled     interfaces
> brtest          8000.00145e992e88       no      pin     eth4
>
>
> The ifup.sh script:
> ifconfig $1 hw ether ee:01:02:03:04:05
> /sbin/ifconfig $1 up
> /usr/sbin/brctl addif brtest $1
>
>
>
>
> --
> Alexey
>



-- 
Regards,

Zhi Yong Wu