Re: [PATCH v1] RDMA/core: Handle ARPHRD_NONE devices for iWARP

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> On Jun 10, 2023, at 8:05 AM, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> 
> On Fri, Jun 09, 2023 at 04:49:49PM -0400, Tom Talpey wrote:
>> On 6/7/2023 3:43 PM, Chuck Lever wrote:
>>> From: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>> 
>>> We would like to enable the use of siw on top of a VPN that is
>>> constructed and managed via a tun device. That hasn't worked up
>>> until now because ARPHRD_NONE devices (such as tun devices) have
>>> no GID for the RDMA/core to look up.
>>> 
>>> But it turns out that the egress device has already been picked for
>>> us. addr_handler() just has to do the right thing with it.
>>> 
>>> Tested with siw and qedr, both initiator and target.
>>> 
>>> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>> ---
>>>  drivers/infiniband/core/cma.c |    3 +++
>>>  1 file changed, 3 insertions(+)
>>> 
>>> This of course needs broader testing, but it seems to work, and it's
>>> a little nicer than "if (dev_type == ARPHRD_NONE)".
>>> 
>>> One thing I discovered is that the NFS/RDMA server implementation
>>> does not deal at all with more than one RDMA device on the system.
>>> I will address that with an ib_client; SunRPC patches forthcoming.
>>> 
>>> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
>>> index 56e568fcd32b..c9a2bdb49e3c 100644
>>> --- a/drivers/infiniband/core/cma.c
>>> +++ b/drivers/infiniband/core/cma.c
>>> @@ -694,6 +694,9 @@ cma_validate_port(struct ib_device *device, u32 port,
>>>   if (!rdma_dev_access_netns(device, id_priv->id.route.addr.dev_addr.net))
>>>   return ERR_PTR(-ENODEV);
>>> + 	if (rdma_protocol_iwarp(device, port))
>>> + 		return rdma_get_gid_attr(device, port, 0);
>> 
>> This might work, but I'm skeptical of the conditional. There's nothing
>> special about iWARP that says a GID should come from the outgoing device
>> mac. And, other protocols without IB GID addressing won't benefit.
> 
> The GID represents the source address, so it better come from the
> outgoing device or something is really wrong.
> 
> iWARP gets a conditional because iwarp always has a single GID, other
> devices do not work that way.

If rdma_get_gid_attr() works for rxe, perhaps we could change
the conditional to match on only software-emulated devices.


--
Chuck Lever






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