netdev - Re: [PATCH net v8 1/2] net/ps3_gelic_net: Fix RX sk

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Date:   Sat, 18 Mar 2023 10:37:28 -0700
From:   Geoff Levand <geoff@...radead.org>
To:     Alexander H Duyck <alexander.duyck@...il.com>,
        netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net v8 1/2] net/ps3_gelic_net: Fix RX sk_buff length

Hi,

Sorry for the delay in my reply, I was away last weekend and
couldn't do any PS3 work.

On 3/11/23 14:37, Alexander H Duyck wrote:
> On Sat, 2023-03-11 at 21:46 +0000, Geoff Levand wrote:
>> The Gelic Ethernet device needs to have the RX sk_buffs aligned to
>> GELIC_NET_RXBUF_ALIGN, and also the length of the RX sk_buffs must
>> be a multiple of GELIC_NET_RXBUF_ALIGN.
>>
>> The current Gelic Ethernet driver was not allocating sk_buffs large
>> enough to allow for this alignment.
>>
>> Also, correct the maximum and minimum MTU sizes, and add a new
>> preprocessor macro for the maximum frame size, GELIC_NET_MAX_FRAME.
>>
>> Fixes various randomly occurring runtime network errors.
>>
>> Fixes: 02c1889166b4 ("ps3: gigabit ethernet driver for PS3, take3")
>> Signed-off-by: Geoff Levand <geoff@...radead.org>
>> ---
>>  drivers/net/ethernet/toshiba/ps3_gelic_net.c | 21 +++++++++++---------
>>  drivers/net/ethernet/toshiba/ps3_gelic_net.h |  5 +++--
>>  2 files changed, 15 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.c b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
>> index cf8de8a7a8a1..56557fc8d18a 100644
>> --- a/drivers/net/ethernet/toshiba/ps3_gelic_net.c
>> +++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
>> @@ -44,6 +44,14 @@ MODULE_AUTHOR("SCE Inc.");
>>  MODULE_DESCRIPTION("Gelic Network driver");
>>  MODULE_LICENSE("GPL");
>>  
>> +/**
>> + * Gelic RX sk_buffs must be aligned to GELIC_NET_RXBUF_ALIGN and the length
>> + * must be a multiple of GELIC_NET_RXBUF_ALIGN.
>> + */
>> +
>> +static const unsigned int gelic_rx_skb_size =
>> +	ALIGN(GELIC_NET_MAX_FRAME, GELIC_NET_RXBUF_ALIGN) +
>> +	GELIC_NET_RXBUF_ALIGN - 1;
>>
> 
> After a bit more digging I now understand the need for the
> "GELIC_NET_RXBUF_ALIGN - 1". It shouldn't be added here. The device
> will not be able to DMA into it. It is being used to align the buffer
> itself to 128B. I am assuming it must be 128B aligned in BOTH size and
> offset.

I want gelic_rx_skb_size to be the value to use with netdev_alloc_skb.

Also, I think just using GELIC_NET_MAX_FRAME for dma_map_single is
enough. Using gelic_rx_skb_size for dma_map_single would work, but the
gelic hardware device could only fill GELIC_NET_MAX_FRAME of the
bigger gelic_rx_skb_size DMA mapping.

>>  /* set irq_mask */
>>  int gelic_card_set_irq_mask(struct gelic_card *card, u64 mask)
>> @@ -370,21 +378,16 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
>>  				  struct gelic_descr *descr)
>>  {
>>  	int offset;
>> -	unsigned int bufsize;
>>  
>>  	if (gelic_descr_get_status(descr) !=  GELIC_DESCR_DMA_NOT_IN_USE)
>>  		dev_info(ctodev(card), "%s: ERROR status\n", __func__);
>> -	/* we need to round up the buffer size to a multiple of 128 */
>> -	bufsize = ALIGN(GELIC_NET_MAX_MTU, GELIC_NET_RXBUF_ALIGN);
>>  
>> -	/* and we need to have it 128 byte aligned, therefore we allocate a
>> -	 * bit more */
>> -	descr->skb = dev_alloc_skb(bufsize + GELIC_NET_RXBUF_ALIGN - 1);
>> +	descr->skb = netdev_alloc_skb(*card->netdev, gelic_rx_skb_size);
> 
> I would leave the "+  GELIC_NET_RXBUF_ALIGN - 1" here. so it should be
> 	descr->skb = netdev_alloc_skb(*card->netdev, 		
> 				      gelic_rx_skb_size +
> 				      GELIC_NET_RXBUF_ALIGN - 1);
> 
> Also I would leav the comment as it makes it a bit clearer what is
> going on here.

With the use of GELIC_NET_MAX_FRAME as the DMA mapping size
gelic_rx_skb_size becomes local to the gelic_descr_prepare_rx
routine, so I put the comment about the size requirements into
the the comment for the gelic_descr_prepare_rx routine.

> 
>>  	if (!descr->skb) {
>>  		descr->buf_addr = 0; /* tell DMAC don't touch memory */
>>  		return -ENOMEM;
>>  	}
>> -	descr->buf_size = cpu_to_be32(bufsize);
>> +	descr->buf_size = cpu_to_be32(gelic_rx_skb_size);
>>  	descr->dmac_cmd_status = 0;
>>  	descr->result_size = 0;
>>  	descr->valid_size = 0;
> 
> The part I missed was the lines of code that didn't make it into the
> patch that like between the two code blocks here above and below. They
> are doing an AND with your align mask and then adding the difference to
> the skb reserve to pad it to be 128B aligned.
> 
>> @@ -397,7 +400,7 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
>>  	/* io-mmu-map the skb */
>>  	descr->buf_addr = cpu_to_be32(dma_map_single(ctodev(card),
>>  						     descr->skb->data,
>> -						     GELIC_NET_MAX_MTU,
>> +						     gelic_rx_skb_size,
>>  						     DMA_FROM_DEVICE));
>>  	if (!descr->buf_addr) {
>>  		dev_kfree_skb_any(descr->skb);
>> @@ -915,7 +918,7 @@ static void gelic_net_pass_skb_up(struct gelic_descr *descr,
>>  	data_error = be32_to_cpu(descr->data_error);
>>  	/* unmap skb buffer */
>>  	dma_unmap_single(ctodev(card), be32_to_cpu(descr->buf_addr),
>> -			 GELIC_NET_MAX_MTU,
>> +			 gelic_rx_skb_size,
>>  			 DMA_FROM_DEVICE);
>>  
>>  	skb_put(skb, be32_to_cpu(descr->valid_size)?
>> diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.h b/drivers/net/ethernet/toshiba/ps3_gelic_net.h
>> index 68f324ed4eaf..0d98defb011e 100644
>> --- a/drivers/net/ethernet/toshiba/ps3_gelic_net.h
>> +++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.h
>> @@ -19,8 +19,9 @@
>>  #define GELIC_NET_RX_DESCRIPTORS        128 /* num of descriptors */
>>  #define GELIC_NET_TX_DESCRIPTORS        128 /* num of descriptors */
>>  
>> -#define GELIC_NET_MAX_MTU               VLAN_ETH_FRAME_LEN
>> -#define GELIC_NET_MIN_MTU               VLAN_ETH_ZLEN
>> +#define GELIC_NET_MAX_FRAME             2312
>> +#define GELIC_NET_MAX_MTU               2294
>> +#define GELIC_NET_MIN_MTU               64
>>  #define GELIC_NET_RXBUF_ALIGN           128
>>  #define GELIC_CARD_RX_CSUM_DEFAULT      1 /* hw chksum */
>>  #define GELIC_NET_WATCHDOG_TIMEOUT      5*HZ

-Geoff