Michael S. Tsirkin
2022-Aug-15 15:52 UTC
[PATCH 2/2] vDPA: conditionally read fields in virtio-net dev
On Mon, Aug 15, 2022 at 05:26:38PM +0800, Zhu Lingshan wrote:> Some fields of virtio-net device config space are > conditional on the feature bits, the spec says: > > "The mac address field always exists > (though is only valid if VIRTIO_NET_F_MAC is set)" > > "max_virtqueue_pairs only exists if VIRTIO_NET_F_MQ > or VIRTIO_NET_F_RSS is set" > > "mtu only exists if VIRTIO_NET_F_MTU is set" > > so we should read MTU, MAC and MQ in the device config > space only when these feature bits are offered. > > For MQ, if both VIRTIO_NET_F_MQ and VIRTIO_NET_F_RSS are > not set, the virtio device should have > one queue pair as default value, so when userspace querying queue pair numbers, > it should return mq=1 than zero. > > For MTU, if VIRTIO_NET_F_MTU is not set, we should not read > MTU from the device config sapce. > RFC894 <A Standard for the Transmission of IP Datagrams over Ethernet Networks> > says:"The minimum length of the data field of a packet sent over an > Ethernet is 1500 octets, thus the maximum length of an IP datagram > sent over an Ethernet is 1500 octets. Implementations are encouraged > to support full-length packets" > > virtio spec says:"The virtio network device is a virtual ethernet card", > so the default MTU value should be 1500 for virtio-net. > > For MAC, the spec says:"If the VIRTIO_NET_F_MAC feature bit is set, > the configuration space mac entry indicates the ?physical? address > of the network card, otherwise the driver would typically > generate a random local MAC address." So there is no > default MAC address if VIRTIO_NET_F_MAC not set. > > This commits introduces functions vdpa_dev_net_mtu_config_fill() > and vdpa_dev_net_mac_config_fill() to fill MTU and MAC. > It also fixes vdpa_dev_net_mq_config_fill() to report correct > MQ when _F_MQ is not present. > > These functions should check devices features than driver > features, and struct vdpa_device is not needed as a parameter > > The test & userspace tool output: > > Feature bit VIRTIO_NET_F_MTU, VIRTIO_NET_F_RSS, VIRTIO_NET_F_MQ > and VIRTIO_NET_F_MAC can be mask out by hardcode. > > However, it is challenging to "disable" the related fields > in the HW device config space, so let's just assume the values > are meaningless if the feature bits are not set. > > Before this change, when feature bits for RSS, MQ, MTU and MAC > are not set, iproute2 output: > $vdpa vdpa0: mac 00:e8:ca:11:be:05 link up link_announce false mtu 1500 > negotiated_featureswhere does it get 1500? what if there's e.g. 0 in the mtu field?> without this commit, function vdpa_dev_net_config_fill() > reads all config space fields unconditionally, so let's > assume the MAC and MTU are meaningless, and it checks > MQ with driver_features, so we don't see max_vq_pairs. > > After applying this commit, when feature bits for > MQ, RSS, MAC and MTU are not set,iproute2 output: > $vdpa dev config show vdpa0 > vdpa0: link up link_announce false max_vq_pairs 1 mtu 1500 > negotiated_features > > As explained above: > Here is no MAC, because VIRTIO_NET_F_MAC is not set, > and there is no default value for MAC. It shows > max_vq_paris = 1 because even without MQ feature, > a functional virtio-net must have one queue pair. > mtu = 1500 is the default value as ethernet > required. > > This commit also add supplementary comments for > __virtio16_to_cpu(true, xxx) operations in > vdpa_dev_net_config_fill() and vdpa_fill_stats_rec() > > Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com> > --- > drivers/vdpa/vdpa.c | 60 +++++++++++++++++++++++++++++++++++---------- > 1 file changed, 47 insertions(+), 13 deletions(-) > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c > index efb55a06e961..a74660b98979 100644 > --- a/drivers/vdpa/vdpa.c > +++ b/drivers/vdpa/vdpa.c > @@ -801,19 +801,44 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callba > return msg->len; > } > > -static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev, > - struct sk_buff *msg, u64 features, > +static int vdpa_dev_net_mq_config_fill(struct sk_buff *msg, u64 features, > const struct virtio_net_config *config) > { > u16 val_u16; > > - if ((features & BIT_ULL(VIRTIO_NET_F_MQ)) == 0) > - return 0; > + if ((features & BIT_ULL(VIRTIO_NET_F_MQ)) == 0 && > + (features & BIT_ULL(VIRTIO_NET_F_RSS)) == 0) > + val_u16 = 1; > + else > + val_u16 = __virtio16_to_cpu(true, config->max_virtqueue_pairs); > > - val_u16 = le16_to_cpu(config->max_virtqueue_pairs); > return nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MAX_VQP, val_u16); > } > > +static int vdpa_dev_net_mtu_config_fill(struct sk_buff *msg, u64 features, > + const struct virtio_net_config *config) > +{ > + u16 val_u16; > + > + if ((features & BIT_ULL(VIRTIO_NET_F_MTU)) == 0) > + val_u16 = 1500; > + else > + val_u16 = __virtio16_to_cpu(true, config->mtu); > + > + return nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16); > +} > + > +static int vdpa_dev_net_mac_config_fill(struct sk_buff *msg, u64 features, > + const struct virtio_net_config *config) > +{ > + if ((features & BIT_ULL(VIRTIO_NET_F_MAC)) == 0) > + return 0; > + else > + return nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, > + sizeof(config->mac), config->mac); > +} > + > + > static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg) > { > struct virtio_net_config config = {}; > @@ -822,18 +847,16 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms > > vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config)); > > - if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac), > - config.mac)) > - return -EMSGSIZE; > + /* > + * Assume little endian for now, userspace can tweak this for > + * legacy guest support. > + */ > + val_u16 = __virtio16_to_cpu(true, config.status); > > val_u16 = __virtio16_to_cpu(true, config.status); > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16)) > return -EMSGSIZE; > > - val_u16 = __virtio16_to_cpu(true, config.mtu); > - if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16)) > - return -EMSGSIZE; > - > features_driver = vdev->config->get_driver_features(vdev); > if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver, > VDPA_ATTR_PAD)) > @@ -846,7 +869,13 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms > VDPA_ATTR_PAD)) > return -EMSGSIZE; > > - return vdpa_dev_net_mq_config_fill(vdev, msg, features_driver, &config); > + if (vdpa_dev_net_mac_config_fill(msg, features_device, &config)) > + return -EMSGSIZE; > + > + if (vdpa_dev_net_mtu_config_fill(msg, features_device, &config)) > + return -EMSGSIZE; > + > + return vdpa_dev_net_mq_config_fill(msg, features_device, &config); > } > > static int > @@ -914,6 +943,11 @@ static int vdpa_fill_stats_rec(struct vdpa_device *vdev, struct sk_buff *msg, > } > vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config)); > > + /* > + * Assume little endian for now, userspace can tweak this for > + * legacy guest support. > + */ > + > max_vqp = __virtio16_to_cpu(true, config.max_virtqueue_pairs); > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MAX_VQP, max_vqp)) > return -EMSGSIZE; > -- > 2.31.1