>-----Original Message-----
>From: Andre Przywara [mailto:andre.przyw...@arm.com]
>Sent: Tuesday, July 21, 2015 5:45 PM
>To: Du, Fan; Will Deacon
>Cc: kvm@vger.kernel.org; Marc Zyngier
>Subject: Re: [PATCHv3 2/2] kvmtool: Restrict virtio queue number to 1 when
>vhost on
>
>Hi,
>
>On 21/07/15 07:18, Fan Du wrote:
>> vhost kernel driver does not support mutiple queue yet,
>> Tweak queue number will fail with "--net mode=tap,vhost=1,mq=2"
>> as below when lkvm trying to set ring kick fd for queue 2:
>>
>> VHOST_SET_VRING_KICK failed: No buffer space available
>>
>> Error on this scenario, and overide with the default one queue
>> configuration.
>
>I don't like the idea of overriding an explicitly given command line
>parameter (mq=2).
>So why do you provide mq=2 in the first place if you know that the
>kernel does not support it?
On the contrary, the help message doesn't explicitly state mq is not supported
when vhost=1, what's the insanity to supply with mq option?!
>I'd rather see the error message to be more descriptive in that case.
>That would help the user to understand what's going on, also it would
>still work should the kernel ever support multiple queues in the future.
I will check how it could be support, either in user land or kernel.
So let's drop this patch.
>Cheers,
>Andre.
>
>>
>> Signed-off-by: Fan Du <fan...@intel.com>
>> ---
>> virtio/net.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/virtio/net.c b/virtio/net.c
>> index d343615..21a80f3 100644
>> --- a/virtio/net.c
>> +++ b/virtio/net.c
>> @@ -730,6 +730,10 @@ static int set_net_param(struct kvm *kvm, struct
>virtio_net_params *p,
>> p->mq = atoi(val);
>> } else
>> die("Unknown network parameter %s", param);
>> + if (p->vhost && p->mq > 1) {
>> + p->mq = 1;
>> + pr_err("vhost does not support mq yet, overide mq to 1.");
>> + }
>>
>> return 0;
>> }
>>
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