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

From: Alexander Duyck <[email-masked]>
Date: Mon, 30 Mar 2015 08:10:15 -0700

On 03/30/2015 06:53 AM, Vlad Zolotarov wrote:
>
>
> 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

Agreed, just export the _locked functions and drop the _locked extension.

- Alex