Re: vhost-net patches

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 22, 2009 at 10:23:44AM -0700, Shirley Ma wrote:
> On Thu, 2009-10-22 at 15:13 +0200, Michael S. Tsirkin wrote:
> > OK, I sent a patch that should fix the errors for you.
> > Could you please confirm, preferably on-list, whether
> > the patch makes the errors go away for you with
> > userspace virtio?
> 
> Confirmed, your patch has fixed irq handler mismatch errors.
> 
> > However, as I said previously, it's good to fix them but I think
> > they are unrelated to the fact that vhost does not work
> > for you.
> 
> Yes, agreed. One observation is when I enable PCI MSI in guest kernel, I
> found that even without vhost supportin host kernel the network doesn't
> work either.

Yes, but that's on Avi's qemu-kvm.git, so probably merge problems again.

> So I think this is nothing related to vhost. I need to find
> why PCI MSI doesn't work for me.

Probably just bisect until you find the bad commit.

> > Shirley, if you have the time, please send details
> > on your setup and observations on tcpdump output
> > in both guest and host with vhost enabled.
> 
> Yes, here are details:
> 
> HW and distros:
> T61 laptop, cpu is 
> vendor_id	: GenuineIntel
> cpu family	: 6
> model		: 15
> model name	: Intel(R) Core(TM)2 Duo CPU     T7700  @ 2.40GHz
> stepping	: 11
> cpu MHz		: 2393.902
> cache size	: 4096 KB
> 
> Guest installed Fedora 10, Host installed Fedora 10 and updated to
> Fedora11, both doesn't work with guest kernel MSI enabled w/i, w/o vhost
> support.

So, IIUC, my tree with MSI without vhost works?

> 
> Source trees:
> clone your qemu-kvm and vhost git. host kernel is vhost git, guest
> kernel 2.6.32-rc5
> 
> Compile option:
> qemu: ./configure (default target-list = x86_64-softmmu)
> guest kernel: PCI MSI, virio enabled
> host kernel: vhost, kvm, evenfd all enabled
> 
> I tried tap, raw, vnet0, eth0,

what are vnet0 and eth0?
Do you have a bridge in host?
What do brctl show and ifconfig -a show in host?

> here are some qemu commandline example:
> 
> mst/qemu-kvm/x86_64-softmmu/qemu-system-x86_64
> -s /home/xma/images/fedora10-2-vm -name guest2 -boot c -M pc -m 512 -smp
> 1 -monitor pty -drive
> file=/home/xma/images/fedora10-2-vm,if=virtio,boot=on -net
> raw,ifname=eth0 -net nic,macaddr=54:52:00:46:26:80,model=virtio,vhost
> 
> mst/qemu-kvm/x86_64-softmmu/qemu-system-x86_64
> -s /home/xma/images/fedora10-2-vm -name guest2 -boot c -M pc -m 512 -smp
> 1 -monitor pty -drive
> file=/home/xma/images/fedora10-2-vm,if=virtio,boot=on -net
> raw,ifname=vnet0 -net nic,model,macaddr=54:52:00:46:26:80=virtio,vhost 
> 
> Please let me know what I can do next. I am eager to test the vhost
> performance for both latency and bw.
> tcpdump output:
> When I ping from guest to host, I didn't see any packets from any
> interfaces, not even an arp request.
> 
> When I ping from host to guest, guest interface didn't see any packets
> either, not even an arp request.

Did you try tcpdump on the tap interface in host?

> Thanks for your help!
> Shirley
> 
> 
> 
> 

Possibly we'll have to debug this in vhost in host kernel.
I would debug this directly, it's just that my setup is somehow
different and I do not see this issue, otherwise I would not
waste your time.

Can we add some printks?
handle_tx has this at the top:

        if (!sock || !sock_writeable(sock->sk))
                return;

Could you please add

 printk(KERN_ERR "%s: !sock = %d, !sock || !sock_writeable(sock->sk) =
%d",
        __func__, !sock , !sock || !sock_writeable(sock->sk));

*Before* these checks?
Then make modules modules_install
rmmod vhost_net
insmod vhost_net
and re-run.
If you want me to send a patch that does this, let me know please.

Thanks!
-- 
MST