Re: [Qemu-devel] [PATCH 10/12] virtio-net: multiqueue support

[Jason Wang]

On 01/08/2013 06:00 PM, Wanlong Gao wrote:
> On 01/08/2013 05:51 PM, Jason Wang wrote:
>> On 01/08/2013 05:49 PM, Wanlong Gao wrote:
>>> On 01/08/2013 05:29 PM, Jason Wang wrote:
>>>> On 01/08/2013 05:07 PM, Wanlong Gao wrote:
>>>>> On 12/28/2012 06:32 PM, Jason Wang wrote:
>>>>>> +    } else if (nc->peer->info->type !=  NET_CLIENT_OPTIONS_KIND_TAP) {
>>>>>> +        ret = -1;
>>>>>> +    } else {
>>>>>> +        ret = tap_detach(nc->peer);
>>>>>> +    }
>>>>>> +
>>>>>> +    return ret;
>>>>>> +}
>>>>>> +
>>>>>> +static void virtio_net_set_queues(VirtIONet *n)
>>>>>> +{
>>>>>> +    int i;
>>>>>> +
>>>>>> +    for (i = 0; i < n->max_queues; i++) {
>>>>>> +        if (i < n->curr_queues) {
>>>>>> +            assert(!peer_attach(n, i));
>>>>>> +        } else {
>>>>>> +            assert(!peer_detach(n, i));
>>>>> I got a assert here,
>>>>> qemu-system-x86_64: /work/git/qemu/hw/virtio-net.c:330: 
>>>>> virtio_net_set_queues: Assertion `!peer_detach(n, i)' failed.
>>>>>
>>>>> Any thoughts?
>>>>>
>>>>> Thanks,
>>>>> Wanlong Gao
>>>> Thanks for the testing, which steps or cases did you met this assertion,
>>>> migration, reboot or just changing the number of virtqueues?
>>> I use the 3.8-rc2 to test it again, I saw this tag has the multi-tap 
>>> support.
>>>
>>> I just can't start the QEMU use  -netdev 
>>> tap,id=hostnet0,queues=2,fd=%d,fd=%d -device 
>>> virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:ce:7b:29,bus=pci.0,addr=0x3
>>>
>>> I pre-opened two tap fds, did I missing something?
>> Nothing missed :) It should work.
>>
>> Could you please try not use fd=X and let qemu to create the file
>> descriptors by itself? Btw, how did you create the two tap fds?
> Can it create descriptors itself? I get 
> qemu-system-x86_64: -netdev tap,id=hostnet0,queues=2: Device 'tap' could not 
> be initialized

You need prepare an ifup script which default at /etc/qemu-ifup (like
following). Or you may try to add a script=no after:

#!/bin/sh

switch=kvmbr0

/sbin/ifconfig $1 0.0.0.0 up
/usr/sbin/brctl addif $switch $1
/usr/sbin/brctl stp $switch off

This will let qemu create a tap fd itself and make it to be connected to
a port of the bridge caled kvmbr0.
>
> I create the tap fd like this, and dup create the second fd, third fd, right?

The second and third fd should be created with TUNSETIFF with the same
tap_name also. Btw, you need to specify a IFF_MULTI_QUEUE flag to tell
the kernel you want to create a multiqueue tap device, otherwise the
second and third calling of TUNSETIFF will fail.

Thanks
>
>       int tap_fd = open("/dev/net/tun", O_RDWR);
>       int vhost_fd = open("/dev/vhost-net", O_RDWR);
>       char *tap_name = "tap";
>       char cmd[2048];
>       char brctl[256];
>       char netup[256];
>       struct ifreq ifr;
>       if (tap_fd < 0) {
>               printf("open tun device failed\n");
>               return -1;
>       }
>       if (vhost_fd < 0) {
>               printf("open vhost-net device failed\n");
>               return -1;
>       }
>       memset(&ifr, 0, sizeof(ifr));
>       memcpy(ifr.ifr_name, tap_name, sizeof(tap_name));
>       ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
>
>       /*
>        * setup tap net device
>        */
>       if (ioctl(tap_fd, TUNSETIFF, &ifr) < 0) {
>               printf("setup tap net device failed\n");
>               return -1;
>       }
>
>       sprintf(brctl, "brctl addif virbr0 %s", tap_name);
>       sprintf(netup, "ifconfig %s up", tap_name);
>       system(brctl);
>       system(netup);
>
> Thanks,
> Wanlong Gao
>
>
>> Thanks
>>> Thanks,
>>> Wanlong Gao
>>>
>>>>>> +        }
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +static void virtio_net_set_multiqueue(VirtIONet *n, int multiqueue, int 
>>>>>> ctrl);
>>>>>> +
>>>>> --
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>>