Re: [dpdk-dev] [RFC 3/3] net/virtio: add MAC device config getter and setter

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <mcoqueli@redhat.com>
> Sent: Thursday, June 3, 2021 10:29 PM
> To: Xia, Chenbo <chenbo.xia@intel.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; dev@dpdk.org; amorenoz@redhat.com;
> david.marchand@redhat.com
> Subject: Re: [RFC 3/3] net/virtio: add MAC device config getter and setter
> 
> Hi Chenbo,
> 
> On 4/19/21 8:24 AM, Xia, Chenbo wrote:
> > Hi Maxime,
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> >> Sent: Friday, March 19, 2021 6:35 AM
> >> To: dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; amorenoz@redhat.com;
> >> david.marchand@redhat.com
> >> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> >> Subject: [RFC 3/3] net/virtio: add MAC device config getter and setter
> >>
> >> This patch uses the new device config ops to get and set
> >> the MAC address if supported.
> >>
> >> If a valid MAC address is passed as devarg of the
> >> Virtio-user PMD, the driver will try to store it in the
> >> device config space. Otherwise the one provided in
> >> the device config space will be used, if available.
> >
> > I agree with the MAC selection strategy you proposed.
> >
> >>
> >> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> >> ---
> >>  .../net/virtio/virtio_user/virtio_user_dev.c  | 78 ++++++++++++++++---
> >>  .../net/virtio/virtio_user/virtio_user_dev.h  |  2 +
> >>  drivers/net/virtio/virtio_user_ethdev.c       |  7 +-
> >>  3 files changed, 74 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> >> b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> >> index 8757a23f6e..61517692b3 100644
> >> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> >> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> >> @@ -259,20 +259,76 @@ int virtio_user_stop_device(struct virtio_user_dev
> *dev)
> >>  	return -1;
> >>  }
> >>
> >> -static inline void
> >> -parse_mac(struct virtio_user_dev *dev, const char *mac)
> >> +int
> >> +virtio_user_dev_set_mac(struct virtio_user_dev *dev)
> >>  {
> >> -	struct rte_ether_addr tmp;
> >> +	int ret = 0;
> >>
> >> -	if (!mac)
> >> -		return;
> >> +	if (!(dev->device_features & (1ULL << VIRTIO_NET_F_MAC)))
> >> +		return -ENOTSUP;
> >> +
> >> +	if (!dev->ops->set_config)
> >> +		return -ENOTSUP;
> >> +
> >> +	ret = dev->ops->set_config(dev, dev->mac_addr,
> >> +			offsetof(struct virtio_net_config, mac),
> >> +			RTE_ETHER_ADDR_LEN);
> >> +	if (ret)
> >> +		PMD_DRV_LOG(ERR, "(%s) Failed to set MAC address in device\n",
> >> dev->path);
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +int
> >> +virtio_user_dev_get_mac(struct virtio_user_dev *dev)
> >> +{
> >> +	int ret = 0;
> >> +
> >> +	if (!(dev->device_features & (1ULL << VIRTIO_NET_F_MAC)))
> >> +		return -ENOTSUP;
> >> +
> >> +	if (!dev->ops->get_config)
> >> +		return -ENOTSUP;
> >> +
> >> +	ret = dev->ops->get_config(dev, dev->mac_addr,
> >> +			offsetof(struct virtio_net_config, mac),
> >> +			RTE_ETHER_ADDR_LEN);
> >> +	if (ret)
> >> +		PMD_DRV_LOG(ERR, "(%s) Failed to get MAC address from device\n",
> >> dev->path);
> >>
> >> -	if (rte_ether_unformat_addr(mac, &tmp) == 0) {
> >> -		memcpy(dev->mac_addr, &tmp, RTE_ETHER_ADDR_LEN);
> >> +	return ret;
> >> +}
> >> +
> >> +static void
> >> +virtio_user_dev_init_mac(struct virtio_user_dev *dev, const char *mac)
> >> +{
> >> +	struct rte_ether_addr cmdline_mac;
> >> +	int ret;
> >> +
> >> +	if (mac && rte_ether_unformat_addr(mac, &cmdline_mac) == 0) {
> >> +		/*
> >> +		 * MAC address was passed from command-line, try to store
> >> +		 * it in the device if it supports it. Otherwise try to use
> >> +		 * the device one.
> >> +		 */
> >> +		memcpy(dev->mac_addr, &cmdline_mac, RTE_ETHER_ADDR_LEN);
> >>  		dev->mac_specified = 1;
> >
> > How do we define mac_specified? If I understand correctly, it means the mac
> > we see is from device (we set it or we just use device's). Then 'dev-
> >mac_specified = 1'
> > should be after get_mac succeeds.
> 
> You are correct, mac_specified=1 means either user or device specified
> MAC address. If get_mac fails below then we use the user specified MAC
> address, so mac_specified = 1 is still valid in this case.
> 
> > Note that during virtio_user_dev_init, we also use
> > this val to set VIRTIO_NET_F_MAC. But here the val is set without making
> sure the
> > feature exists.
> 
> I am not sure to get youre point, but it sets VIRTIO_NET_F_MAC in the
> frontend features there, that does not mean the feature is negotiated in
> the end.

I think you are correct, I may misunderstood something when I review this first
time. And I want to make sure we are on the same page: since 'mac_specified=1'
will set VIRTIO_NET_F_MAC in frontend_features, so only when user don't set mac
and we don't get mac in device will lead to this feature unsupported, right?

> 
> >> +
> >> +		/* Setting MAC may fail, continue to get the device one in this
> >> case */
> >> +		virtio_user_dev_set_mac(dev);
> >> +		ret = virtio_user_dev_get_mac(dev);
> >> +		if (ret == -ENOTSUP)
> >> +			return;
> >> +
> >> +		if (memcmp(&cmdline_mac, dev->mac_addr, RTE_ETHER_ADDR_LEN))
> >> +			PMD_DRV_LOG(INFO, "(%s) Device MAC update failed\n", dev-
> >>> path);
> >
> > Besides Adrian's comments, if we decide to return no error on this, it may
> also
> > be good to add something like 'using random MAC' to tell users that the
> driver will
> > use random mac. Adding here or in the function that generates mac is both ok.
> 
> If it fails here, it won't be using a random MAC, but the MAC provided
> by the user. The log could be improved with something like:
> "Device MAC update failed, using MAC xx:xx:xx:xx:xx"

Yeah! That's good.

Thanks,
Chenbo

> 
> What do you think?
> 
> > The patchset overall looks good to me. I'm looking forward to v1 😊
> >
> > Thanks,
> > Chenbo
> 
> Thanks,
> Maxime