netdev - Re: [PATCH net-next v9 5/7] ixgbe: Add GET_RSS_KEY command to VF-PF channel commands set

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Date:	Mon, 30 Mar 2015 13:41:26 +0300
From:	Vlad Zolotarov <vladz@...udius-systems.com>
To:	Alexander Duyck <alexander.duyck@...il.com>, netdev@...r.kernel.org
CC:	jeffrey.t.kirsher@...el.com, avi@...udius-systems.com,
	gleb@...udius-systems.com
Subject: Re: [PATCH net-next v9 5/7] ixgbe: Add GET_RSS_KEY command to VF-PF
 channel commands set



On 03/30/15 01:04, Alexander Duyck wrote:
> On 03/29/2015 09:11 AM, Vlad Zolotarov wrote:
>> For 82599 and x540 VFs and PF share the same RSS Key. Therefore we will return
>> the same RSS key for all VFs.
>>
>> Support for other devices will be added later.
>>
>> Signed-off-by: Vlad Zolotarov <vladz@...udius-systems.com>
>> ---
>> New in v9:
>>     - Reduce the support to 82599 and x540 devices only.
>>     - Get rid of registers access in GET_VF_RSS_KEY flow:
>>        - Get the RSS HASH Key value from the PF's adapter->rss_key[].
>>
>> New in v5:
>>     - Use a newly added netdev op to allow/prevent the RSS Hash Key querying on a per-VF
>>       basis.
>>
>> New in v3:
>>     - Added a support for x550 devices.
>>
>> New in v1 (compared to RFC):
>>     - Use "if-else" statement instead of a "switch-case" for a single option case
>>       (in ixgbe_get_vf_rss_key()).
>> ---
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_mbx.h   |  1 +
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c | 25 +++++++++++++++++++++++++
>>   2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_mbx.h b/drivers/net/ethernet/intel/ixgbe/ixgbe_mbx.h
>> index 3522f53..b1e4703 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_mbx.h
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_mbx.h
>> @@ -100,6 +100,7 @@ enum ixgbe_pfvf_api_rev {
>>   
>>   /* mailbox API, version 1.2 VF requests */
>>   #define IXGBE_VF_GET_RETA	0x0a	/* VF request for RETA */
>> +#define IXGBE_VF_GET_RSS_KEY	0x0b	/* get RSS key */
>>   
>>   /* length of permanent address message returned from PF */
>>   #define IXGBE_VF_PERMADDR_MSG_LEN 4
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
>> index 8424e7f..4d87458 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
>> @@ -996,6 +996,28 @@ static int ixgbe_get_vf_reta(struct ixgbe_adapter *adapter, u32 *msgbuf, u32 vf)
>>   	return 0;
>>   }
>>   
>> +static int ixgbe_get_vf_rss_key(struct ixgbe_adapter *adapter,
>> +				u32 *msgbuf, u32 vf)
>> +{
>> +	struct ixgbe_hw *hw = &adapter->hw;
>> +	u32 *rss_key = &msgbuf[1];
>> +
>> +	/* verify the PF is supporting the correct API */
>> +	if (!adapter->vfinfo[vf].rss_query_enabled ||
>> +	    (adapter->vfinfo[vf].vf_api != ixgbe_mbox_api_12))
>> +		return -EPERM;
>> +
>> +	/* Read the RSS KEY.
>> +	 * We only support 82599 and x540 devices at the moment.
>> +	 */
>> +	if (hw->mac.type >= ixgbe_mac_X550)
>> +		return -1;
>> +
> The return should be not supported, not -1 since that is too ambiguous.

By the way, this (-1) didn't come from nowhere - I looked at other 
functions in this file (e.g. ixgbe_get_vf_queues() and 
ixgbe_negotiate_vf_api()) and they are returning
this "ambiguous" (-1) just fine in the situations where -EOPNOTSUPP and 
-EINVAL (correspondingly) would be much more appropriate.
So, I went and checked who was the guy who added this terrible 
"ambiguity" and, surprise-surprise!!!, it was mister Alexander Duyck! :D 
In both (!!!) cases! Bang-bang!!! :D Of course it was "two years ago" 
Alex but still... ;)

Anyway, since we fight the ambiguity now I think u, guys, would like to 
send a cleanup follow-up patches that would adjust your "ambiguous code" 
with the new "super-clear styling" we are introducing in this patches... ;)

>
>> +	memcpy(rss_key, adapter->rss_key, sizeof(adapter->rss_key));
>> +
>> +	return 0;
>> +}
>> +
>>   static int ixgbe_rcv_msg_from_vf(struct ixgbe_adapter *adapter, u32 vf)
>>   {
>>   	u32 mbx_size = IXGBE_VFMAILBOX_SIZE;
>> @@ -1055,6 +1077,9 @@ static int ixgbe_rcv_msg_from_vf(struct ixgbe_adapter *adapter, u32 vf)
>>   	case IXGBE_VF_GET_RETA:
>>   		retval = ixgbe_get_vf_reta(adapter, msgbuf, vf);
>>   		break;
>> +	case IXGBE_VF_GET_RSS_KEY:
>> +		retval = ixgbe_get_vf_rss_key(adapter, msgbuf, vf);
>> +		break;
>>   	default:
>>   		e_err(drv, "Unhandled Msg %8.8x\n", msgbuf[0]);
>>   		retval = IXGBE_ERR_MBX;
>>

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