Re: [PATCH v5 for-next 3/3] IB/core: Obtain subnet_prefix from cache in IB devices

[Anand Khoje]

On 6/22/2021 5:19 AM, Jason Gunthorpe wrote:
> On Wed, Jun 16, 2021 at 09:15:09PM +0530, Anand Khoje wrote:
> >   
> > @@ -1523,13 +1524,21 @@ static int config_non_roce_gid_cache(struct ib_device *device,
> >   	device->port_data[port].cache.lmc = tprops->lmc;
> >   	device->port_data[port].cache.port_state = tprops->state;
> >   
> > -	device->port_data[port].cache.subnet_prefix = tprops->subnet_prefix;
> > +	ret = rdma_query_gid(device, port, 0, &gid);
> > +	if (ret) {
>
> This is quite a bit different than just calling ops.query_gid() - why
> are you changing it? I'm not sure all the additional tests will pass,
> the 0 gid entry is not required to be valid..
Hi Jason,

We have opted for rdma_query_gid(), as during ib_cache_update() the code 
calls ops.query_gid() earlier in config_non_roce_gid_cache(), thereby 
updating the value of GID in cache. We utilize this updated value, 
instead of calling ops->query_gid() again.

 	I'm not sure all the additional tests will pass,
 	the 0 gid entry is not required to be valid..

To get subnet_prefix __ib_query_port() does indeed obtain zero index GID.

https://elixir.bootlin.com/linux/v5.13-rc5/source/drivers/infiniband/core/device.c#L2067

> > @@ -1629,6 +1638,7 @@ int ib_cache_setup_one(struct ib_device *device)
> >   		err = ib_cache_update(device, p, true, true, true);
> >   		if (err)
> >   			return err;
> > +		device->port_data[p].cache_is_initialized = 1;
> >   	}
>
> And I would much prefer things be re-organized so the cache can be
> valid sooner to adding this variable. What is the earlier call that is
> motivating this?
>
> Jason

During device load and when cache is yet to be updated, ib_query_port() 
should have a mechanism to identify if the cache entry is valid or 
invalid (uninitialized), we have added this variable just to ensure the 
validity of cache.

Thanks,
Anand