> -----Original Message----- > From: Konstantin Taranov <kotaranov@xxxxxxxxxxxxx> > Sent: Wednesday, June 26, 2024 2:20 PM > To: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>; Leon Romanovsky > <leon@xxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Cc: Konstantin Taranov <kotaranov@xxxxxxxxxxxxxxxxxxx>; Wei Hu > <weh@xxxxxxxxxxxxx>; sharmaajay@xxxxxxxxxxxxx; Long Li > <longli@xxxxxxxxxxxxx>; jgg@xxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; linux- > netdev <netdev@xxxxxxxxxxxxxxx> > Subject: Re: [PATCH rdma-next 1/1] RDMA/mana_ib: Set correct device into > ib > > > > > > On Wed, Jun 26, 2024 at 09:05:05AM +0000, Konstantin Taranov > wrote: > > > > > > > > When mc->ports[0] is not slave, use it in the set_netdev. > > > > > > > > When mana is used in netvsc, the stored net devices in mana > > > > > > > > are slaves and GIDs should be taken from their master > devices. > > > > > > > > In the baremetal case, the mc->ports devices will not be > slaves. > > > > > > > > > > > > > > I wonder, why do you have "... | IFF_SLAVE" in > > > > > > > __netvsc_vf_setup() in a first place? Isn't IFF_SLAVE is > supposed to > > be set by bond driver? > > > > > > > > > > > > > > > > > > > I guess it is just a valid use of the IFF_SLAVE bit. In the > bond > > > > > > case it is also set as a BOND netdev. The IFF_SLAVE helps to > show > > users that another master > > > > > > netdev should be used for networking. But I am not an expert in > > netvsc. > > > > > > > > > > The thing is that netvsc is virtual device like many others, but > > > > > it is the only one who uses IFF_SLAVE bit. The comment around > that > > > > > bit says "slave of a load balancer.", which is not the case > > > > > according to the Hyper-V documentation. > > > > > > > > > > You will need to get Ack from netdev maintainers to rely on > > > > > IFF_SLAVE bit in the way you are relying on it now. > > > > > > > > This is used to tell userspace tools to not interact directly with > the device. > > > > For example, it is used when VF is connected to netvsc device. > > > > It prevents things like IPv6 local address, and Network Manager > won't > > modify device. > > > > > > You described how hyper-v uses it, but I'm interested to get > > > acknowledgment that it is a valid use case for IFF_SLAVE, despite > sentence > > written in the comment. > > > > There is no documented semantics around any of the IF flags, only > historical > > precedent used by bond, team and bridge drivers. Initially Hyper-V VF > used > > bonding but it was impossibly difficult to make this work across all > versions of > > Linux, so transparent VF support was added instead. Ideally, the VF > device > > could be hidden from userspace but that required more kernel > modifications > > than would be accepted. > > Thanks Stephen for the explanation! > > I am also CCing Haiyang, who maintains Hyper-V netvsc. > Yes, netvsc sets the IFF_SLAVE on VF for the bonding. Acked-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
