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Jason Wang

2018-Jun-12 01:54 UTC

[Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net

On 2018?06?12? 01:26, Michael S. Tsirkin wrote:> On Mon, May 07, 2018 at 04:09:54PM -0700, Sridhar Samudrala wrote:
>> This feature bit can be used by hypervisor to indicate virtio_net
device to
>> act as a standby for another device with the same MAC address.
>>
>> I tested this with a small change to the patch to mark the STANDBY
feature 'true'
>> by default as i am using libvirt to start the VMs.
>> Is there a way to pass the newly added feature bit 'standby' to
qemu via libvirt
>> XML file?
>>
>> Signed-off-by: Sridhar Samudrala <sridhar.samudrala at intel.com>
> So I do not think we can commit to this interface: we
> really need to control visibility of the primary device.
The problem is legacy guest won't use primary device at all if we do this.

How about control the visibility of standby device?

Thanks
> However just for testing purposes, we could add a non-stable
> interface "x-standby" with the understanding that as any
> x- prefix it's unstable and will be changed down the road,
> likely in the next release.
>
>
>> ---
>>   hw/net/virtio-net.c                         | 2 ++
>>   include/standard-headers/linux/virtio_net.h | 3 +++
>>   2 files changed, 5 insertions(+)
>>
>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>> index 90502fca7c..38b3140670 100644
>> --- a/hw/net/virtio-net.c
>> +++ b/hw/net/virtio-net.c
>> @@ -2198,6 +2198,8 @@ static Property virtio_net_properties[] = {
>>                        true),
>>       DEFINE_PROP_INT32("speed", VirtIONet, net_conf.speed,
SPEED_UNKNOWN),
>>       DEFINE_PROP_STRING("duplex", VirtIONet,
net_conf.duplex_str),
>> +    DEFINE_PROP_BIT64("standby", VirtIONet, host_features,
VIRTIO_NET_F_STANDBY,
>> +                      false),
>>       DEFINE_PROP_END_OF_LIST(),
>>   };
>>   
>> diff --git a/include/standard-headers/linux/virtio_net.h
b/include/standard-headers/linux/virtio_net.h
>> index e9f255ea3f..01ec09684c 100644
>> --- a/include/standard-headers/linux/virtio_net.h
>> +++ b/include/standard-headers/linux/virtio_net.h
>> @@ -57,6 +57,9 @@
>>   					 * Steering */
>>   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
>>   
>> +#define VIRTIO_NET_F_STANDBY      62    /* Act as standby for another
device
>> +                                         * with the same MAC.
>> +                                         */
>>   #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed and
duplex */
>>   
>>   #ifndef VIRTIO_NET_NO_LEGACY
>> -- 
>> 2.14.3

Michael S. Tsirkin

2018-Jun-12 02:17 UTC

head link

[Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net

On Tue, Jun 12, 2018 at 09:54:44AM +0800, Jason Wang
wrote:> 
> 
> On 2018?06?12? 01:26, Michael S. Tsirkin wrote:
> > On Mon, May 07, 2018 at 04:09:54PM -0700, Sridhar Samudrala wrote:
> > > This feature bit can be used by hypervisor to indicate virtio_net
device to
> > > act as a standby for another device with the same MAC address.
> > > 
> > > I tested this with a small change to the patch to mark the
STANDBY feature 'true'
> > > by default as i am using libvirt to start the VMs.
> > > Is there a way to pass the newly added feature bit
'standby' to qemu via libvirt
> > > XML file?
> > > 
> > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala at
intel.com>
> > So I do not think we can commit to this interface: we
> > really need to control visibility of the primary device.
> 
> The problem is legacy guest won't use primary device at all if we do
this.
And that's by design - I think it's the only way to ensure the
legacy guest isn't confused.
> How about control the visibility of standby device?
> 
> Thanks
standy the always there to guarantee no downtime.
> > However just for testing purposes, we could add a non-stable
> > interface "x-standby" with the understanding that as any
> > x- prefix it's unstable and will be changed down the road,
> > likely in the next release.
> > 
> > 
> > > ---
> > >   hw/net/virtio-net.c                         | 2 ++
> > >   include/standard-headers/linux/virtio_net.h | 3 +++
> > >   2 files changed, 5 insertions(+)
> > > 
> > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > > index 90502fca7c..38b3140670 100644
> > > --- a/hw/net/virtio-net.c
> > > +++ b/hw/net/virtio-net.c
> > > @@ -2198,6 +2198,8 @@ static Property virtio_net_properties[] = {
> > >                        true),
> > >       DEFINE_PROP_INT32("speed", VirtIONet,
net_conf.speed, SPEED_UNKNOWN),
> > >       DEFINE_PROP_STRING("duplex", VirtIONet,
net_conf.duplex_str),
> > > +    DEFINE_PROP_BIT64("standby", VirtIONet,
host_features, VIRTIO_NET_F_STANDBY,
> > > +                      false),
> > >       DEFINE_PROP_END_OF_LIST(),
> > >   };
> > > diff --git a/include/standard-headers/linux/virtio_net.h
b/include/standard-headers/linux/virtio_net.h
> > > index e9f255ea3f..01ec09684c 100644
> > > --- a/include/standard-headers/linux/virtio_net.h
> > > +++ b/include/standard-headers/linux/virtio_net.h
> > > @@ -57,6 +57,9 @@
> > >   					 * Steering */
> > >   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
> > > +#define VIRTIO_NET_F_STANDBY      62    /* Act as standby for
another device
> > > +                                         * with the same MAC.
> > > +                                         */
> > >   #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed
and duplex */
> > >   #ifndef VIRTIO_NET_NO_LEGACY
> > > -- 
> > > 2.14.3

Samudrala, Sridhar

2018-Jun-12 05:02 UTC

head link

[Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net

On 6/11/2018 7:17 PM, Michael S. Tsirkin wrote:> On Tue, Jun 12, 2018 at 09:54:44AM +0800, Jason Wang wrote:
>>
>> On 2018?06?12? 01:26, Michael S. Tsirkin wrote:
>>> On Mon, May 07, 2018 at 04:09:54PM -0700, Sridhar Samudrala wrote:
>>>> This feature bit can be used by hypervisor to indicate
virtio_net device to
>>>> act as a standby for another device with the same MAC address.
>>>>
>>>> I tested this with a small change to the patch to mark the
STANDBY feature 'true'
>>>> by default as i am using libvirt to start the VMs.
>>>> Is there a way to pass the newly added feature bit
'standby' to qemu via libvirt
>>>> XML file?
>>>>
>>>> Signed-off-by: Sridhar Samudrala <sridhar.samudrala at
intel.com>
>>> So I do not think we can commit to this interface: we
>>> really need to control visibility of the primary device.
>> The problem is legacy guest won't use primary device at all if we
do this.
> And that's by design - I think it's the only way to ensure the
> legacy guest isn't confused.
Yes. I think so. But i am not sure if Qemu is the right place to control the
visibility
of the primary device. The primary device may not be specified as an argument to
Qemu. It
may be plugged in later.
The cloud service provider is providing a feature that enables low latency
datapath and live
migration capability.
A tenant can use this feature only if he is running a VM that has virtio-net
with failover support.

I think Qemu should check if guest virtio-net supports this feature and provide
a mechanism for
an upper layer indicating if the STANDBY feature is successfully negotiated or
not.
The upper layer can then decide if it should hot plug a VF with the same MAC and
manage the 2 links.
If VF is successfully hot plugged, virtio-net link should be disabled.

>
>> How about control the visibility of standby device?
>>
>> Thanks
> standy the always there to guarantee no downtime.
>
>>> However just for testing purposes, we could add a non-stable
>>> interface "x-standby" with the understanding that as any
>>> x- prefix it's unstable and will be changed down the road,
>>> likely in the next release.
>>>
>>>
>>>> ---
>>>>    hw/net/virtio-net.c                         | 2 ++
>>>>    include/standard-headers/linux/virtio_net.h | 3 +++
>>>>    2 files changed, 5 insertions(+)
>>>>
>>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>>>> index 90502fca7c..38b3140670 100644
>>>> --- a/hw/net/virtio-net.c
>>>> +++ b/hw/net/virtio-net.c
>>>> @@ -2198,6 +2198,8 @@ static Property virtio_net_properties[] =
{
>>>>                         true),
>>>>        DEFINE_PROP_INT32("speed", VirtIONet,
net_conf.speed, SPEED_UNKNOWN),
>>>>        DEFINE_PROP_STRING("duplex", VirtIONet,
net_conf.duplex_str),
>>>> +    DEFINE_PROP_BIT64("standby", VirtIONet,
host_features, VIRTIO_NET_F_STANDBY,
>>>> +                      false),
>>>>        DEFINE_PROP_END_OF_LIST(),
>>>>    };
>>>> diff --git a/include/standard-headers/linux/virtio_net.h
b/include/standard-headers/linux/virtio_net.h
>>>> index e9f255ea3f..01ec09684c 100644
>>>> --- a/include/standard-headers/linux/virtio_net.h
>>>> +++ b/include/standard-headers/linux/virtio_net.h
>>>> @@ -57,6 +57,9 @@
>>>>    					 * Steering */
>>>>    #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
>>>> +#define VIRTIO_NET_F_STANDBY      62    /* Act as standby for
another device
>>>> +                                         * with the same MAC.
>>>> +                                         */
>>>>    #define VIRTIO_NET_F_SPEED_DUPLEX 63	/* Device set linkspeed
and duplex */
>>>>    #ifndef VIRTIO_NET_NO_LEGACY
>>>> -- 
>>>> 2.14.3

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