netdev - Re: [PATCH net-next] efx: convert to new udp

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Message-ID: <ecc09a90-1946-fc6a-a5fd-5e0dfe11532d@solarflare.com>
Date:   Tue, 21 Jul 2020 13:05:39 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-net-drivers@...arflare.com>, <mhabets@...arflare.com>,
        <mslattery@...arflare.com>
Subject: Re: [PATCH net-next] efx: convert to new udp_tunnel infrastructure

On 20/07/2020 18:21, Jakub Kicinski wrote:
> On Mon, 20 Jul 2020 12:45:54 +0100 Edward Cree wrote:
>> I think I'd prefer to keep the switch() that explicitlychecks
>>  for UDP_TUNNEL_TYPE_GENEVE; even though the infrastructure
>>  makes sure it won't ever not be, I'd still feel more comfortable
>>  that way.  But it's up to you.
> 
> To me the motivation of expressing capabilities is for the core 
> to be able to do the necessary checking (and make more intelligent
> decisions). All the drivers I've converted make the assumption they
> won't see tunnel types they don't support.

Like I say, up to you.  It's not how I'd write it but if that's how
 you're doing all the drivers then consistency is probably good.

>> Could we not keep a 'valid'/'used' flag in the table, used in
>>  roughly the same way we were checking count != 0?
> 
> How about we do the !port check in efx_ef10_udp_tnl_has_port()?
> 
> Per-entry valid / used flag seems a little wasteful.
> 
> Another option is to have a reserved tunnel type for invalid / unused.

Reserved tunnel type seems best to me.  (sfc generally uses all-ones
 values for reserved, so this would be 0xffff.)

Alternatively you could change it to store an enum efx_encap_type in
 the table (see filter.h), and move the conversion to MCDI values to
 efx_ef10_set_udp_tnl_ports(), since that has a defined NONE value.
 But that means converting twice (from udp_parseable_tunnel_type to
 efx_encap_type and then again to MCDI) which isn't the prettiest.

-ed