Re: [dpdk-dev] [PATCH 1/6] fm10k: Fix improper RX buffer size assignment

["Qiu, Michael" <michael.qiu@intel.com>]

Tested-by: Michael Qiu <michael.qiu@intel.com>

- OS: Fedora20  3.11.10-301
- GCC: gcc version 4.8.3 2014911
- CPU: Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz
- NIC: Ethernet controller: Intel Corporation Device 15a4 (rev 01)
- Default x86_64-native-linuxapp-gcc configuration


On 5/29/2015 4:11 PM, Chen, Jing D wrote:
> From: "Chen Jing D(Mark)" <jing.d.chen@intel.com>
>
> As RX buffer is aligned to 512B within mbuf, some bytes are reserved
> for this purpose, and the worst case could be 511B. But SRR reg
> assumes all buffers have the same size. In order to fill the gap,
> we'll have to consider the worsst case and assume 512B is reserved.
> If we don't do so, it's possible for HW to overwrite data to next
> mbuf.
>
> Signed-off-by: Chen Jing D(Mark) <jing.d.chen@intel.com>
> ---
>  drivers/net/fm10k/fm10k.h        |    5 +++--
>  drivers/net/fm10k/fm10k_ethdev.c |   12 ++++++++++--
>  2 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/fm10k/fm10k.h b/drivers/net/fm10k/fm10k.h
> index 0e31796..ad7a7d1 100644
> --- a/drivers/net/fm10k/fm10k.h
> +++ b/drivers/net/fm10k/fm10k.h
> @@ -191,7 +191,8 @@ struct fm10k_tx_queue {
>  
>  /* enforce 512B alignment on default Rx DMA addresses */
>  #define MBUF_DMA_ADDR_DEFAULT(mb) \
> -	((uint64_t) RTE_ALIGN(((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM), 512))
> +	((uint64_t) RTE_ALIGN(((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM),\
> +			FM10K_RX_DATABUF_ALIGN))
>  
>  static inline void fifo_reset(struct fifo *fifo, uint32_t len)
>  {
> @@ -263,7 +264,7 @@ fm10k_addr_alignment_valid(struct rte_mbuf *mb)
>  	uint64_t boundary1, boundary2;
>  
>  	/* 512B aligned? */
> -	if (RTE_ALIGN(addr, 512) == addr)
> +	if (RTE_ALIGN(addr, FM10K_RX_DATABUF_ALIGN) == addr)
>  		return 1;
>  
>  	/* 8B aligned, and max Ethernet frame would not cross a 4KB boundary? */
> diff --git a/drivers/net/fm10k/fm10k_ethdev.c b/drivers/net/fm10k/fm10k_ethdev.c
> index 275c19c..a5e09a0 100644
> --- a/drivers/net/fm10k/fm10k_ethdev.c
> +++ b/drivers/net/fm10k/fm10k_ethdev.c
> @@ -41,7 +41,6 @@
>  #include "fm10k.h"
>  #include "base/fm10k_api.h"
>  
> -#define FM10K_RX_BUFF_ALIGN 512
>  /* Default delay to acquire mailbox lock */
>  #define FM10K_MBXLOCK_DELAY_US 20
>  #define UINT64_LOWER_32BITS_MASK 0x00000000ffffffffULL
> @@ -426,6 +425,15 @@ fm10k_dev_rx_init(struct rte_eth_dev *dev)
>  		/* Configure the Rx buffer size for one buff without split */
>  		buf_size = (uint16_t)(rte_pktmbuf_data_room_size(rxq->mp) -
>  			RTE_PKTMBUF_HEADROOM);
> +		/* As RX buffer is aligned to 512B within mbuf, some bytes are
> +		 * reserved for this purpose, and the worst case could be 511B.
> +		 * But SRR reg assumes all buffers have the same size. In order
> +		 * to fill the gap, we'll have to consider the worst case and
> +		 * assume 512B is reserved. If we don't do so, it's possible
> +		 * for HW to overwrite data to next mbuf.
> +		 */
> +		buf_size -= FM10K_RX_DATABUF_ALIGN;
> +
>  		FM10K_WRITE_REG(hw, FM10K_SRRCTL(i),
>  				buf_size >> FM10K_SRRCTL_BSIZEPKT_SHIFT);
>  
> @@ -909,7 +917,7 @@ mempool_element_size_valid(struct rte_mempool *mp)
>  			RTE_PKTMBUF_HEADROOM;
>  
>  	/* account for up to 512B of alignment */
> -	min_size -= FM10K_RX_BUFF_ALIGN;
> +	min_size -= FM10K_RX_DATABUF_ALIGN;
>  
>  	/* sanity check for overflow */
>  	if (min_size > mp->elt_size)