Re: vhost-net patches

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

On Tue, Oct 20, 2009 at 10:14:55AM -0700, Shirley Ma wrote:
> 
> Hello Michael,
> 
> >what is vnet->vector?
> >And what do you mean by not defined?
> 
> In funcation:
> 
> static int vhost_virtqueue_init()
> {
> ......
>               r = vdev->binding->irqfd(vdev->binding_opaque, q->vector,
> vq->call);
> ......
> }.....
> 
> q->vector is 65535,

Thanks for debugging this.
I think this means that guest does not use MSI-X.

You can verify this by booting guest without vhost,
and performing the following command:
	 cat /proc/interrupts

Please note that you currently need recent kernel in guest,
so that it uses MSI-X. I plan on implementing regular IRQ,
but not yet, and it will be slower anyway.

> in   static int virtio_pci_irqfd()
> {
> ......
>     if (vector >= proxy->pci_dev.msix_entries_nr) {
>         fprintf(stderr, " pci irq fd returned vector %d, msix_entries_nr %d
> \n",
>                 vector, proxy->pci_dev.msix_entries_nr); <------- I added
> one output line here.
>         return -EINVAL;
> ....
> }...
> The output is:
> 
>        pci irq fd returned vector 65535, msix_entries_nr 3, EINVAL is
> returned.
> 
> thanks
> Shirley Ma
> IBM Linux Technology Center
> 15300 SW Koll Parkway
> Beaverton, OR 97006-6063
> Phone(Fax): (503) 578-7638
> 
> 
> 
> 
>                                                                        
>              "Michael S.                                               
>              Tsirkin"                                                  
>              <mst@redhat.com>                                           To
>                                        Shirley Ma/Beaverton/IBM@IBMUS  
>              10/20/2009 04:34                                           cc
>              AM                        sri@linux.vnet.ibm.com, David   
>                                        Stevens/Beaverton/IBM@IBMUS,    
>                                        kvm@vger.kernel.org             
>                                                                    Subject
>                                        Re: vhost-net patches           
>                                                                        
>                                                                        
>                                                                        
>                                                                        
>                                                                        
>                                                                        
> 
> 
> 
> 
> On Mon, Oct 19, 2009 at 04:08:24PM -0700, Shirley Ma wrote:
> > Hello Michael,
> >
> > >They all failed with the following error
> > >    vhost_net_init returned -7
> > >This is an error message from hw/virtio-net.c:virtio_net_driver_ok()
> when
> > >vhost_net_start() fails. It looks like dev->binding->irqfd() is failing
> in
> > >vhost_virtqueue_init(). Haven't yet debugged further. I have
> CONFIG_EVENTFD
> > >enabled in the host kernel.
> >
> > >From the debug output, looks like the vnet->vector is not defined,
> 
> what is vnet->vector?
> And what do you mean by not defined?
> 
> > and the
> > default msix_entries_nr is 3, so it returned EINVAL from
> virtio_pci_irqfd.
> > Looks we need to either disable QEMU_PCI_CAP_MSIX or define vector in
> QEMU
> > configuration?
> 
> You shouldn't have to do anything.
> 
> > I am not familiar with MSIX stuffs.
> >
> > Thanks
> > Shirley
> >
> >
> > Inactive hide details for sri---10/19/2009 03:56:57 PM---On Sun,
> 2009-10-18 at
> > 19:32 +0200, Michael S. Tsirkin wrote:sri---10/19/2009 03:56:57 PM---On
> Sun,
> > 2009-10-18 at 19:32 +0200, Michael S. Tsirkin wrote:
> >
> >                 sri@linux.vnet.ibm.com [cid]   *
> >                                             To "Michael S. Tsirkin"
> <mst@redhat.com>,
> >                 10/19/2009 03:56 PM            kvm@vger.kernel.org
> >                                        [cid]   *
> >                                             cc David
> Stevens/Beaverton/IBM@IBMUS, Shirley Ma/
> >                                                Beaverton/IBM@IBMUS
> >                                        [cid]   *
> >                                        Subject Re: vhost-net patches
> >                                        *        *
> >
> > On Sun, 2009-10-18 at 19:32 +0200, Michael S. Tsirkin wrote:
> > > On Sun, Oct 18, 2009 at 12:53:56PM +0200, Michael S. Tsirkin wrote:
> > > > On Fri, Oct 16, 2009 at 12:29:29PM -0700, Sridhar Samudrala wrote:
> > > > > Hi Michael,
> > > > >
> > > > > We are trying out your vhost-net patches from your git trees on
> > kernel.org.
> > > > > I am using mst/vhost.git as host kernel and mst/qemu-kvm.git for
> qemu.
> > > > >
> > > > > I am using the following qemu script to start the guest using
> userspace
> > tap backend.
> > > > >
> > > > >
> home/sridhar/git/mst/qemu-kvm/x86_64-softmmu/qemu-system-x86_64 /home/
> > sridhar/kvm_images/fedora10-1-vm -m 512 -drive
> file=/home/sridhar/kvm_images/
> > fedora10-1-vm,if=virtio,index=0,boot=on -net nic,macaddr=
> > 54:52:00:35:e3:73,model=virtio -net
> tap,ifname=vnet0,script=no,downscript=no
> > > > >
> > > > > Now that i got the default backend to work, i wanted to try vhost
> in
> > kernel. But
> > > > > could not figure out the right -net option to pass to qemu.
> > > > >
> > > > > Can you let me know the right syntax to start a guest using vhost.
> > > > >
> > > > > Thanks
> > > > > Sridhar
> > > >
> > > > Here's an example with raw socket:
> > > >
> > > > /root/kvm-test/bin/qemu-system-x86_64 -m 1G -kernel \
> > > > /boot/vmlinuz-$release -append \
> > > > 'root=UUID=d5d2d201-d086-42ad-bb1d-32fbe40eda71 ro quiet nosplash \
> > > > console=tty0 console=ttyS0,9600n8' -initrd /boot/guest-initrd.img \
> > > > $HOME/disk.raw.copy -net raw,ifname=eth3 -net nic,model=virtio,vhost
> \
> > > > -balloon none -redir tcp:8023::22
> > > >
> > > > As you see, I changed the command line.
> > > > You now simply add ",vhost" after model, and it will locate
> > > > host network interface specified earlier and attach to it.
> > > > This should have been clear from running  qemu with -help
> > > > flag. Could you please suggest how can that text
> > > > be clarified?
> >
> > I updated to your latest git trees and the default user-space tap backend
> using
> > the
> > following -net options worked fine.
> > -net tap,ifname=vnet0,script=no,downscript=no -net nic,model=virtio
> >
> > But i could not get vhost to work with either raw or tap backends.
> > I tried the following combinations.
> > 1) -net raw,ifname=eth0 -net nic,model=virtio,vhost
> > 2) -net raw,ifname=vnet0, -net nic,model=virtio,vhost
> > 3) -net tap,ifname=vnet0,script=no,downscript=no -net
> nic,model=virtio,vhost
> 
> Yes, should work.
> 
> >
> > They all failed with the following error
> >    vhost_net_init returned -7
> > This is an error message from hw/virtio-net.c:virtio_net_driver_ok() when
> > vhost_net_start() fails. It looks like dev->binding->irqfd() is failing
> in
> > vhost_virtqueue_init().
> 
> what parameters are passed in?
> 
> > Haven't yet debugged further.
> 
> this calls into virtio_pci_irqfd.
> 
> > I have CONFIG_EVENTFD
> > enabled in the host kernel.
> 
> Note you need to also enable eventfd support under kvm menu.
> 
> > Are all the above -net options supposed to work?
> >
> > In your descriptions, you say that checksum/tso offload is not supported.
> Isn't
> > it
> > possible to send/receive large packets without checksum using AF_PACKET
> sockets
> > if
> > the attached interface supports these offloads.
> > Do you see the same offload issue even when using tap backend via vhost?
> >
> > Thanks
> > Sridhar
> >
> >
> >
> >
> >
> >
> >
> >
>