Re: [PATCH] RDMA/rxe: prevent rxe creation on top of vlan interface

[mohammad <goody698@gmail.com>]

On 8/13/20 6:16 AM, Zhu Yanjun wrote:
> On 8/11/2020 11:04 PM, Mohammad Heib wrote:
>> Creating rxe device on top of vlan interface will create a 
>> non-functional device
>> that has an empty gids table and can't be used for rdma cm 
>> communication.
>
> Can we fix this empty gids table?

I'm not sure if that can be done in the rxe only, since the IP's of the 
netdev enrolls into

the gids table by the ibcore in the device registration 
stage(gid_table_setup_one) and that requires making changes in the ibcore.


we can enroll those IP's into the device gids table after the rxe device 
registration but still

we have to expose some ibcore functions (add_netdev_ips) and track the 
address change events of the

vlan interface and update the gids table accordingly to those IP's changes.

>
> So this gids table can be used for rdma cm communication.
>
> Zhu Yanjun
>
>>
>> This is caused by the logic in 
>> enum_all_gids_of_dev_cb()/is_eth_port_of_netdev(),
>> which only considers networks connected to "upper devices" of the 
>> configured
>> network device, resulting in an empty set of gids for a vlan interface,
>> and attempts to connect via this rdma device fail in 
>> cm_init_av_for_response
>> because no gids can be resolved.
>>
>> apparently, this behavior was implemented to fit the HW-RoCE devices 
>> that create
>> RoCE device per port, therefore RXE must behave the same like HW-RoCE 
>> devices
>> and create rxe device per real device only.
>>
>> In order to communicate via a vlan interface, the user must use the 
>> gid index of
>> the vlan address instead of creating rxe over vlan.
>>
>> Signed-off-by: Mohammad Heib <goody698@gmail.com>
>> ---
>>   drivers/infiniband/sw/rxe/rxe.c       | 6 ++++++
>>   drivers/infiniband/sw/rxe/rxe_sysfs.c | 6 ++++++
>>   2 files changed, 12 insertions(+)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe.c 
>> b/drivers/infiniband/sw/rxe/rxe.c
>> index 5642eefb4ba1..d2076aa7a732 100644
>> --- a/drivers/infiniband/sw/rxe/rxe.c
>> +++ b/drivers/infiniband/sw/rxe/rxe.c
>> @@ -310,6 +310,12 @@ static int rxe_newlink(const char *ibdev_name, 
>> struct net_device *ndev)
>>       struct rxe_dev *exists;
>>       int err = 0;
>>   +    if (is_vlan_dev(ndev)) {
>> +        pr_err("rxe creation allowed on top of a real device only\n");
>> +        err = -EPERM;
>> +        goto err;
>> +    }
>> +
>>       exists = rxe_get_dev_from_net(ndev);
>>       if (exists) {
>>           ib_device_put(&exists->ib_dev);
>> diff --git a/drivers/infiniband/sw/rxe/rxe_sysfs.c 
>> b/drivers/infiniband/sw/rxe/rxe_sysfs.c
>> index ccda5f5a3bc0..0a083c3d900a 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_sysfs.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_sysfs.c
>> @@ -73,6 +73,12 @@ static int rxe_param_set_add(const char *val, 
>> const struct kernel_param *kp)
>>           return -EINVAL;
>>       }
>>   +    if (is_vlan_dev(ndev)) {
>> +        pr_err("rxe creation allowed on top of a real device only\n");
>> +        err = -EPERM;
>> +        goto err;
>> +    }
>> +
>>       exists = rxe_get_dev_from_net(ndev);
>>       if (exists) {
>>           ib_device_put(&exists->ib_dev);
>
>