Subject: Re: [PATCH net-next v9 6/7] ixgbevf: Add RSS Key query code

From: Vlad Zolotarov <[email-masked]>
Date: Mon, 30 Mar 2015 16:53:14 +0300

On 03/30/15 01:04, Alexander Duyck wrote:
> On 03/29/2015 09:11 AM, Vlad Zolotarov wrote:
>> Add the ixgbevf_get_rss_key() function that queries the PF for an RSS Random Key
>> using a new VF-PF channel IXGBE_VF_GET_RSS_KEY command.
>>
>> This patch adds the support for 82599 and x540 devices only. Support for other
>> devices will be added later.
>>
>> Signed-off-by: Vlad Zolotarov <[email-masked]>
>> ---
>> New in v9:
>>     - Reduce the support to 82599 and x540 devices only.
>>     - Added IXGBEVF_RSS_HASH_KEY_SIZE macro.
>>
>> New in v8:
>>     - Protect a mailbox access.
>>
>> New in v6:
>>     - Return a proper return code when an operation is blocked by PF.
>>
>> New in v2:
>>     - Added a more detailed patch description.
>>
>> New in v1 (compared to RFC):
>>     - Use "if-else" statement instead of a "switch-case" for a single option case
>>       (in ixgbevf_get_rss_key()).
>> ---
>>   drivers/net/ethernet/intel/ixgbevf/ixgbevf.h |  1 +
>>   drivers/net/ethernet/intel/ixgbevf/mbx.h     |  1 +
>>   drivers/net/ethernet/intel/ixgbevf/vf.c      | 66 ++++++++++++++++++++++++++++
>>   drivers/net/ethernet/intel/ixgbevf/vf.h      |  1 +
>>   4 files changed, 69 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
>> index bc939a1..6771ae3 100644
>> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
>> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
>> @@ -145,6 +145,7 @@ struct ixgbevf_ring {
>>   #define MAX_RX_QUEUES IXGBE_VF_MAX_RX_QUEUES
>>   #define MAX_TX_QUEUES IXGBE_VF_MAX_TX_QUEUES
>>   #define IXGBEVF_MAX_RSS_QUEUES	2
>> +#define IXGBEVF_RSS_HASH_KEY_SIZE	40
>>   
>>   #define IXGBEVF_DEFAULT_TXD	1024
>>   #define IXGBEVF_DEFAULT_RXD	512
>> diff --git a/drivers/net/ethernet/intel/ixgbevf/mbx.h b/drivers/net/ethernet/intel/ixgbevf/mbx.h
>> index 66e138b..82f44e0 100644
>> --- a/drivers/net/ethernet/intel/ixgbevf/mbx.h
>> +++ b/drivers/net/ethernet/intel/ixgbevf/mbx.h
>> @@ -110,6 +110,7 @@ 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 hash key */
>>   
>>   /* length of permanent address message returned from PF */
>>   #define IXGBE_VF_PERMADDR_MSG_LEN	4
>> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.c b/drivers/net/ethernet/intel/ixgbevf/vf.c
>> index 2676c0b..ec68145 100644
>> --- a/drivers/net/ethernet/intel/ixgbevf/vf.c
>> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.c
>> @@ -301,6 +301,72 @@ static inline int ixgbevf_get_reta_locked(struct ixgbe_hw *hw, u32 *msgbuf,
>>   	return 0;
>>   }
>>   
>> +static inline int ixgbevf_get_rss_key_locked(struct ixgbe_hw *hw, u8 *rss_key)
>> +{
>> +	int err;
>> +	u32 msgbuf[IXGBE_VFMAILBOX_SIZE];
>> +
>> +	/* We currently support the RSS Random Key retrieval for 82599 and x540
>> +	 * devices only.
>> +	 *
>> +	 * Thus return an error if API doesn't support RSS Random Key retrieval
>> +	 * or if the operation is not supported for this device type.
>> +	 */
>> +	if (hw->api_version != ixgbe_mbox_api_12 ||
>> +	    hw->mac.type >= ixgbe_mac_X550_vf)
>> +		return -EPERM;
>> +
> The return type here should be not supported, or IXGBE_NOT_IMPLEMENTED,
> not no permissions.
>
>> +	msgbuf[0] = IXGBE_VF_GET_RSS_KEY;
>> +	err = hw->mbx.ops.write_posted(hw, msgbuf, 1);
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	err = hw->mbx.ops.read_posted(hw, msgbuf, 11);
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	msgbuf[0] &= ~IXGBE_VT_MSGTYPE_CTS;
>> +
>> +	/* If the operation has been refused by a PF return -EPERM */
>> +	if (msgbuf[0] == (IXGBE_VF_GET_RETA | IXGBE_VT_MSGTYPE_NACK))
>> +		return -EPERM;
>> +
>> +	/* If we didn't get an ACK there must have been
>> +	 * some sort of mailbox error so we should treat it
>> +	 * as such.
>> +	 */
>> +	if (msgbuf[0] != (IXGBE_VF_GET_RSS_KEY | IXGBE_VT_MSGTYPE_ACK))
>> +		return IXGBE_ERR_MBX;
>> +
>> +	memcpy(rss_key, msgbuf + 1, IXGBEVF_RSS_HASH_KEY_SIZE);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * ixgbevf_get_rss_key - get the RSS Random Key
>> + * @hw: pointer to the HW structure
>> + * @reta: buffer to fill with RETA contents.
>> + *
>> + * The "rss_key" buffer should be big enough to contain 10 registers.
>> + * Ensures the atomicy of a mailbox access using the adapter.mbx_lock spinlock.
>> + *
>> + * Returns: 0 on success.
>> + *          if API doesn't support this operation - (-EPERM).
>> + */
>> +int ixgbevf_get_rss_key(struct ixgbevf_adapter *a, u8 *rss_key)
>> +{
>> +	int rc;
>> +
>> +	spin_lock_bh(&a->mbx_lock);
>> +	rc = ixgbevf_get_rss_key_locked(&a->hw, rss_key);
>> +	spin_unlock_bh(&a->mbx_lock);
>> +
>> +	return rc;
>> +}
>> +
> Since there is currently no cases where you would be getting the rss_key
> without the RETA you might just want to combine this function with
> ixgbevf_get_reta so you only take the lock once and process both
> messages in one pass instead of having to bounce the spinlock.

I'd rather not do this.
Let's start from the beginning: the locks here should be removed and
added at the caller level to match what u wrote about patch04.
Then about the uniting the two functions mentioned above - there isn't
any added value of doing this. Taking a lock only once may be done
without uniting (see PATCH07 in v10 series).
On the other hand, this uniting is going to make the code awkward and
unclear ("why are these together anyway?").
So, I'd rather keep these functions as they are apart from fixing the locking issue. I'll essentially export the _locked functions.

thanks,
vlad

>
>>   /**
>>    * ixgbevf_get_reta - get the RSS redirection table (RETA) contents.
>>    * @adapter: pointer to the port handle
>> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.h b/drivers/net/ethernet/intel/ixgbevf/vf.h
>> index 7944962..a054716 100644
>> --- a/drivers/net/ethernet/intel/ixgbevf/vf.h
>> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.h
>> @@ -212,4 +212,5 @@ int ixgbevf_negotiate_api_version(struct ixgbe_hw *hw, int api);
>>   int ixgbevf_get_queues(struct ixgbe_hw *hw, unsigned int *num_tcs,
>>   		       unsigned int *default_tc);
>>   int ixgbevf_get_reta(struct ixgbevf_adapter *adapter, u32 *reta);
>> +int ixgbevf_get_rss_key(struct ixgbevf_adapter *adapter, u8 *rss_key);
>>   #endif /* __IXGBE_VF_H__ */
>>