Re: RSS configuration in iwlwifi

[Ben Hutchings <ben@decadent.org.uk>]

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On Wed, 2016-04-20 at 16:22 +0000, Grumbach, Emmanuel wrote:
> On Wed, 2016-04-20 at 16:47 +0100, Ben Hutchings wrote:
> > 
> > On Wed, 2016-04-20 at 15:30 +0000, Grumbach, Emmanuel wrote:
> > > 
> > > Hi Ben,
> > > 
> > > 
> > > Thanks for looking at our code.
> > > 
> > > 
> > > On Wed, 2016-04-20 at 16:08 +0100, Ben Hutchings wrote:
> > > > 
> > > > 
> > > > I'm not sure if you were aware, but there is a standard API for
> > > > configuring RSS in network drivers, part of ethtool_ops.  I think
> > > > iwlwifi should implement that rather than a driver-specific
> > > > debugfs
> > > > interface.
> > > > 
> > > You are right, this is why Sara made this commit:
> > > 
> > > commit 854d773e4ab5869200004af4ca5d851730849903
> > > Author: Sara Sharon <sara.sharon@intel.com>
> > > Date:   Tue Mar 22 15:55:58 2016 +0200
> > > 
> > >     iwlwifi: mvm: improve RSS configuration
> > >     
> > >     Improve current RSS configuration:
> > >      * Use netdev_rss_key instead of keeping a local copy.
> > >      * Configure also UDP hashing to have UDP traffic spread across
> > > queues.
> > >      Do not direct RSS traffic to our fallback queue.
> > > 
> > >     Signed-off-by: Sara Sharon <sara.sharon@intel.com>
> > >     Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
> > That doesn't really address what I said.  Yes, it's using the common
> > RSS key, but it's not implementing the ethtool operations to get and
> > set the indirection table and the types of flow hashing that are
> > enabled.
> > 
> Hm.. I think that setting the indirection table is a problem in our
> case because the PN check is done in the driver. The PN check is the
> way WiFi addresses the replay attack, and since the PN check relies on
> per-cpu variables, we cannot *safely* allow users to modify the
> indirection table while traffic is flowing.

I see.  You could make this work when the interface is down and return
-EBUSY if the interface is up.

Ben.

-- 
Ben Hutchings
Never attribute to conspiracy what can adequately be explained by stupidity.

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