netdev - Re: [PATCH net-next 1/2] virtio_net: Introduce VIRTIO_NET_F

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Date:   Wed, 3 Jan 2018 10:17:50 -0800
From:   "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     stephen@...workplumber.org, netdev@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com
Subject: Re: [PATCH net-next 1/2] virtio_net: Introduce VIRTIO_NET_F_MASTER
 feature bit



On 1/3/2018 9:43 AM, Michael S. Tsirkin wrote:
> On Tue, Jan 02, 2018 at 04:35:37PM -0800, Sridhar Samudrala wrote:
>> This feature bit can be used by hypervisor to indicate virtio_net device to
>> act as a master for a directly attached passthru device with the same MAC
>> address.
>>
>> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
>> ---
>>   drivers/net/virtio_net.c        | 3 ++-
>>   include/uapi/linux/virtio_net.h | 1 +
>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 6fb7b658a6cc..46844a1d9a62 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -2796,7 +2796,8 @@ static struct virtio_device_id id_table[] = {
>>   	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
>>   	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
>>   	VIRTIO_NET_F_CTRL_MAC_ADDR, \
>> -	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>> +	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
>> +	VIRTIO_NET_F_MASTER
>>   
>>   static unsigned int features[] = {
>>   	VIRTNET_FEATURES,
>> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
>> index fc353b518288..a9b4e0836786 100644
>> --- a/include/uapi/linux/virtio_net.h
>> +++ b/include/uapi/linux/virtio_net.h
>> @@ -56,6 +56,7 @@
>>   #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
>>   					 * Steering */
>>   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
>> +#define VIRTIO_NET_F_MASTER	62	/* act as master for a VF device */
> Well the virtio hardware doesn't really know whether it's a master or
> the slave of a bond. In fact quite possibly down the road we'll add a
> virtual device on top as others seem to want to do - that other one will
> be the master then.
>
> And we do nothing do check it's a VF.
>
> So maybe a better name would be
>
> #define VIRTIO_NET_F_BACKUP	62	/* Act as backup for another device with the same MAC */
Yes. BACKUP  does make more sense as virtio is only used as a BACKUP 
datapath when the other
device is unplugged.


>
>>   
>>   #ifndef VIRTIO_NET_NO_LEGACY
>>   #define VIRTIO_NET_F_GSO	6	/* Host handles pkts w/ any GSO type */
>> -- 
>> 2.14.3