Re: [PATCH RFC 0/3] Support standard SRIOV configuration for IB VFs

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, May 26, 2015 at 12:50:52AM +0300, Or Gerlitz wrote:
> On Tue, May 26, 2015 at 12:14 AM, Jason Gunthorpe
> <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote:
> > On Mon, May 25, 2015 at 11:04:41PM +0300, Or Gerlitz wrote:
> >
> >> OK, so rewinding a bit, the IB VF [1] identity is their 8 bytes port
> >> GUID, and as Jason noted the user/kernel API allows to deliver up to
> >> 32 bytes between user and kernel under the set_vf_mac flow
> >> (do_setvfinfo() in net/core/rtnetlink.c). Trying it out through
> >> **non-modified** ip tool and net/core/rtnetlink.c things just work -
> >> I can set eight bytes value to be the virtual port GUID :
> >
> > Was I not perfectly clear? You have to use the 20 byte LLADDR format here:
> >
> >> # ip link set dev ib0 vf 1 mac aa:bb:cc:dd:ee:ff:11:22
> 
> Jason,
> 
> I am aiming to provision the VF IB end-node address == port GUID (vGUID)
> in the same manner that VF Eth end-node address is their MAC, not
> more, not less.

I perfectly understand what you are trying to do.

I care about the design and consistency of netlink - and that means
there is one LLADDR definition for a net device, and every single netlink
message that touches a LLADDR uses that definition - for IPoIB that is 20
bytes.

To violate that design invariant needs an incredibly strong argument,
and you haven't made it.

This allows generic code to work with the LLADDR - for instance 'ip
link set vf mac' should have checked the size of the IFLA_ADDRESS and
demanded that the address argument is the same number of bytes. It is
very broken the command happily accepts an 8 byte and 6 byte argument
for the same device.

Yes, it is ugly that the PF side's ndo_get_vf_config cannot return the
same 20 byte address of the VF's ipoib interface, but I think that is
less ugly than forcing a different address format just for the vf calls.

If you have doubts then *ask netdev*. Ask them if ndo_set_vf_mac must
follow the same address size and format as IFLA_ADDRESS, or if we can
use something else.

Such a netlink architecture choice is beyond the authority of
linux-rdma.

Jason
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