Date:	Wed, 31 Dec 2014 10:00:36 -0800
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Vlad Zolotarov <vladz@...udius-systems.com>, netdev@...r.kernel.org
CC:	gleb@...udius-systems.com, avi@...udius-systems.com,
	jeffrey.t.kirsher@...el.com,
	Don Skidmore <donald.c.skidmore@...el.com>,
	"tantilov, Emil S" <emil.s.tantilov@...el.com>
Subject: Re: [PATCH net-next v1 2/5] ixgbevf: Add a RETA query code

I suspect this code is badly broken as it doesn't take several things
into account.

First the PF redirection table can have values outside of the range
supported by the VF.  This is allowed as the VF can set how many bits of
the redirection table it actually wants to use.  This is controlled via
the PSRTYPE register.  So for example the PF can be running with 4
queues, and the VF can run either in single queue or as just a pair of
queues.

Second you could compress this data much more tightly by taking
advantage of the bit widths allowed.  So for everything x540 and older
they only use a 4 bit value per entry.  That means you could
theoretically stuff 8 entries per u32 instead of just 4.  Though I am
not sure if that even really matters since we only care about the last
bit anyway since we should only support RSS for up to 2 queues on the
VFs (IRQ limitation).  You might be able to just get away with a 128b
vector containing a single bit per RSS entry since that is all the VFs
normally will use.

The third issue I see is that this set of patches seem to completely
ignore the X550.  The X550 has a much larger RETA on the PF, and I
believe it does something different for the VF in terms of RSS though I
don't recall exactly what the differences are.

- Alex

On 12/31/2014 01:51 AM, Vlad Zolotarov wrote:
>    - Added a new API version support.
>    - Added the query implementation in the ixgbevf.
>
> Signed-off-by: Vlad Zolotarov <vladz@...udius-systems.com>
> ---
> New in v1 (compared to RFC):
>    - Use "if-else" statement instead of a "switch-case" for a single option case
>      (in ixgbevf_get_reta()).
> ---
>  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c |  4 +-
>  drivers/net/ethernet/intel/ixgbevf/mbx.h          |  6 ++
>  drivers/net/ethernet/intel/ixgbevf/vf.c           | 73 +++++++++++++++++++++++
>  drivers/net/ethernet/intel/ixgbevf/vf.h           |  1 +
>  4 files changed, 83 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> index 62a0d8e..ba6ab61 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
> @@ -1880,7 +1880,8 @@ static void ixgbevf_init_last_counter_stats(struct ixgbevf_adapter *adapter)
>  static void ixgbevf_negotiate_api(struct ixgbevf_adapter *adapter)
>  {
>  	struct ixgbe_hw *hw = &adapter->hw;
> -	int api[] = { ixgbe_mbox_api_11,
> +	int api[] = { ixgbe_mbox_api_12,
> +		      ixgbe_mbox_api_11,
>  		      ixgbe_mbox_api_10,
>  		      ixgbe_mbox_api_unknown };
>  	int err = 0, idx = 0;
> @@ -3525,6 +3526,7 @@ static int ixgbevf_change_mtu(struct net_device *netdev, int new_mtu)
>  
>  	switch (adapter->hw.api_version) {
>  	case ixgbe_mbox_api_11:
> +	case ixgbe_mbox_api_12:
>  		max_possible_frame = IXGBE_MAX_JUMBO_FRAME_SIZE;
>  		break;
>  	default:
> diff --git a/drivers/net/ethernet/intel/ixgbevf/mbx.h b/drivers/net/ethernet/intel/ixgbevf/mbx.h
> index 0bc3005..3e148a8 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/mbx.h
> +++ b/drivers/net/ethernet/intel/ixgbevf/mbx.h
> @@ -86,6 +86,7 @@ enum ixgbe_pfvf_api_rev {
>  	ixgbe_mbox_api_10,	/* API version 1.0, linux/freebsd VF driver */
>  	ixgbe_mbox_api_20,	/* API version 2.0, solaris Phase1 VF driver */
>  	ixgbe_mbox_api_11,	/* API version 1.1, linux/freebsd VF driver */
> +	ixgbe_mbox_api_12,	/* API version 1.2, linux/freebsd VF driver */
>  	/* This value should always be last */
>  	ixgbe_mbox_api_unknown,	/* indicates that API version is not known */
>  };
> @@ -104,6 +105,11 @@ enum ixgbe_pfvf_api_rev {
>  /* mailbox API, version 1.1 VF requests */
>  #define IXGBE_VF_GET_QUEUE	0x09 /* get queue configuration */
>  
> +/* mailbox API, version 1.2 VF requests */
> +#define IXGBE_VF_GET_RETA_0	0x0a /* get RETA[0..11]  */
> +#define IXGBE_VF_GET_RETA_1	0x0b /* get RETA[12..23] */
> +#define IXGBE_VF_GET_RETA_2	0x0c /* get RETA[24..31] */
> +
>  /* GET_QUEUES return data indices within the mailbox */
>  #define IXGBE_VF_TX_QUEUES	1	/* number of Tx queues supported */
>  #define IXGBE_VF_RX_QUEUES	2	/* number of Rx queues supported */
> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.c b/drivers/net/ethernet/intel/ixgbevf/vf.c
> index cdb53be..8b98cdf 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/vf.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.c
> @@ -258,6 +258,78 @@ static s32 ixgbevf_set_uc_addr_vf(struct ixgbe_hw *hw, u32 index, u8 *addr)
>  	return ret_val;
>  }
>  
> +static inline int _ixgbevf_get_reta(struct ixgbe_hw *hw, u32 *msgbuf,
> +				    u32 *reta, u32 op, int reta_offset_dw,
> +				    size_t dwords)
> +{
> +	int err;
> +
> +	msgbuf[0] = op;
> +	err = hw->mbx.ops.write_posted(hw, msgbuf, 1);
> +
> +	if (err)
> +		return err;
> +
> +	err = hw->mbx.ops.read_posted(hw, msgbuf, 1 + dwords);
> +
> +	if (err)
> +		return err;
> +
> +	msgbuf[0] &= ~IXGBE_VT_MSGTYPE_CTS;
> +
> +	/* 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] != (op | IXGBE_VT_MSGTYPE_ACK))
> +		return IXGBE_ERR_MBX;
> +
> +	memcpy(reta + reta_offset_dw, msgbuf + 1, 4 * dwords);
> +
> +	return 0;
> +}
> +
> +/**
> + * ixgbevf_get_reta - get the RSS redirection table (RETA) contents.
> + * @hw: pointer to the HW structure
> + * @reta: buffer to fill with RETA contents.
> + *
> + * The "reta" buffer should be big enough to contain 32 registers.
> + *
> + * Returns: 0 on success.
> + *          if API doesn't support this operation - (-EPERM).
> + */
> +int ixgbevf_get_reta(struct ixgbe_hw *hw, u32 *reta)
> +{
> +	int err;
> +	u32 msgbuf[IXGBE_VFMAILBOX_SIZE];
> +
> +	/* Return an error if API doesn't RETA querying. */
> +	if (hw->api_version != ixgbe_mbox_api_12)
> +		return -EPERM;
> +
> +	/* Fetch RETA from the PF. We do it in 3 steps due to mailbox size
> +	 * limitation - we can bring up to 15 dwords every time while RETA
> +	 * consists of 32 dwords. Therefore we'll bring 12, 12 and 8 dwords in
> +	 * each step correspondingly.
> +	 */
> +
> +	/* RETA[0..11] */
> +	err = _ixgbevf_get_reta(hw, msgbuf, reta, IXGBE_VF_GET_RETA_0, 0, 12);
> +	if (err)
> +		return err;
> +
> +	/* RETA[12..23] */
> +	err = _ixgbevf_get_reta(hw, msgbuf, reta, IXGBE_VF_GET_RETA_1, 12, 12);
> +	if (err)
> +		return err;
> +
> +	/* RETA[24..31] */
> +	err = _ixgbevf_get_reta(hw, msgbuf, reta, IXGBE_VF_GET_RETA_2, 24, 8);
> +
> +	return err;
> +}
> +
>  /**
>   *  ixgbevf_set_rar_vf - set device MAC address
>   *  @hw: pointer to hardware structure
> @@ -545,6 +617,7 @@ int ixgbevf_get_queues(struct ixgbe_hw *hw, unsigned int *num_tcs,
>  	/* do nothing if API doesn't support ixgbevf_get_queues */
>  	switch (hw->api_version) {
>  	case ixgbe_mbox_api_11:
> +	case ixgbe_mbox_api_12:
>  		break;
>  	default:
>  		return 0;
> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.h b/drivers/net/ethernet/intel/ixgbevf/vf.h
> index 5b17242..73c1b33 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/vf.h
> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.h
> @@ -208,5 +208,6 @@ void ixgbevf_rlpml_set_vf(struct ixgbe_hw *hw, u16 max_size);
>  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 ixgbe_hw *hw, u32 *reta);
>  #endif /* __IXGBE_VF_H__ */
>  

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