Re: [dpdk-dev] [PATCH 1/3] ethdev: add RSS hash level

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 12/7/19 10:56 PM, Ajit Khaparde wrote:
> On Sat, Dec 7, 2019 at 1:14 AM Andrew Rybchenko <arybchenko@solarflare.com>
> wrote:
> 
>> On 12/7/19 3:59 AM, Ajit Khaparde wrote:
>>> This patch adds ability to configure RSS hash level in hardware.
>>> This feature will allow an application to select RSS hash calculation
>>> on outer or inner headers for tunneled packets.
>>>
>>> Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
>>> ---
>>>   lib/librte_ethdev/rte_ethdev.h | 27 +++++++++++++++++++++++++++
>>>   1 file changed, 27 insertions(+)
>>>
>>> diff --git a/lib/librte_ethdev/rte_ethdev.h
>> b/lib/librte_ethdev/rte_ethdev.h
>>> index 18a9defc2..5189bdbab 100644
>>> --- a/lib/librte_ethdev/rte_ethdev.h
>>> +++ b/lib/librte_ethdev/rte_ethdev.h
>>> @@ -444,11 +444,35 @@ struct rte_vlan_filter_conf {
>>>    * The *rss_hf* field of the *rss_conf* structure indicates the
>> different
>>>    * types of IPv4/IPv6 packets to which the RSS hashing must be applied.
>>>    * Supplying an *rss_hf* equal to zero disables the RSS feature.
>>> + *
>>> + * The *rss_level* field of the *rss_conf* structure indicates the
>>> + * Packet encapsulation level RSS hash @p types apply to.
>>> + *
>>> + * - @p 0 requests the default behavior. Depending on the packet
>>> + *   type, it can mean outermost, innermost, anything in between or
>>> + *   even no RSS.
>>> + *
>>> + *   It basically stands for the innermost encapsulation level RSS
>>> + *   can be performed on according to PMD and device capabilities.
>>> + *
>>> + * - @p 1 requests RSS to be performed on the outermost packet
>>> + *   encapsulation level.
>>> + *
>>> + * - @p 2 and subsequent values request RSS to be performed on the
>>> + *   specified inner packet encapsulation level, from outermost to
>>> + *   innermost (lower to higher values).
>>> + *
>>> + * Support for values other than @p 0 is dependent on the underlying
>>> + * hardware in use.
>>> + *
>>> + * Requesting a specific RSS level on unrecognized traffic results
>>> + * in undefined behavior.
>>>    */
>>>   struct rte_eth_rss_conf {
>>>       uint8_t *rss_key;    /**< If not NULL, 40-byte hash key. */
>>>       uint8_t rss_key_len; /**< hash key length in bytes. */
>>>       uint64_t rss_hf;     /**< Hash functions to apply - see below. */
>>> +     uint32_t rss_level;  /**< RSS hash level */
>>>   };
>>
>> I'm not sure that offload flag is required in this case.
>> I think maximum supported rss_level in dev_info will provide
> 
> more information and per-queue level does not make sense

I think information about maximum RSS hash level could be
useful. At least it provides clear information about
limitations instead of attempt to configure with RSS level
equal to 3 and getting error without clear understanding why
if the level is not supported.

>> in this case. Even if per-queue group control is required,
>> it should be doable via rte_flow API RSS action.
>>
> This is dev config and not flow specific configuration. Ofcourse while
> passing
> the rss_config, not all the queues may be specified, but that is not a new
> behavior and it is upto the application anyway.

Yes, of course. I was just trying to explain why Rx offload is
not required and it should be just dev_info field with maximum
RSS level supported.

> Are we transitioning the device level configuration to rte_flow/flow
> based scheme?

No-no, see above.

>> Anyway, it looks like it is ABI breakage with all consequences.
>> In 64-bit case it is possible to put it before rss_hf to avoid
>> ABI breakage, but it will break ABI on 32-bit anyway.
>>
> Right.
> I sent the proposal for review early to get it cleaned up and ready
> when the window opens.

OK, good.

>>
>>>   /*
>>> @@ -599,6 +623,8 @@ rte_eth_rss_hf_refine(uint64_t rss_hf)
>>>       ETH_RSS_GENEVE | \
>>>       ETH_RSS_NVGRE)
>>>
>>> +#define ETH_RSS_LEVEL_DEFAULT        0
>>> +
>>>   /*
>>>    * Definitions used for redirection table entry size.
>>>    * Some RSS RETA sizes may not be supported by some drivers, check the
>>> @@ -1103,6 +1129,7 @@ struct rte_eth_conf {
>>>   #define DEV_RX_OFFLOAD_SCTP_CKSUM   0x00020000
>>>   #define DEV_RX_OFFLOAD_OUTER_UDP_CKSUM  0x00040000
>>>   #define DEV_RX_OFFLOAD_RSS_HASH             0x00080000
>>> +#define DEV_RX_OFFLOAD_RSS_LEVEL     0x00100000
>>>
>>>   #define DEV_RX_OFFLOAD_CHECKSUM (DEV_RX_OFFLOAD_IPV4_CKSUM | \
>>>                                DEV_RX_OFFLOAD_UDP_CKSUM | \
>>>
>>
>>