[PATCH] net/mana: fix wrong indexing on CQE error when coalescing is used

[Ferruh Yigit]

On 7/7/2023 7:01 PM, Long Li wrote:
>> Subject: Re: [PATCH] net/mana: fix wrong indexing on CQE error when coalescing
>> is used
>>
>> On 7/7/2023 1:17 AM, longli at linuxonhyperv.com wrote:
>>> From: Long Li <longli at microsoft.com>
>>>
>>> On a fatal CQE error when coalescing is used, update the correct index
>>> and allow proceeding to the next CQE.
>>>
>>> Fixes: 3409e0f172f6 ("net/mana: implement Rx CQE coalescing")
>>>
>>
>> Is above fixes commit correct?
>> Logic for 'CQE_RX_COALESCED_4' is not changed with this commit, in above
>> commit and in this commit both does breaks the loop.
> 
> Yes, the "Fixes" tag is correct. Here CQE_RX_COALESCED_4 is rearranged to make it easier to read, but it doesn't change the behavior.
> 
>>
>> This commit changes logic for 'CQE_RX_TRUNCATED' and 'default' cases, which
>> are added with different commits, not the one in fixes line.
>>
>> "fatal CQE error when coalescing" mentioned in the commit log, to which switch
>> case does this corresponds to?
> 
> The previous patch (3409e0f172f6 ) introduced variable "i", an index to completion CQEs. But both 'default' and 'CQE_RX_TRUNCATED' cases don't advance "i", hence not advance to next CQE on error.
> 

Right, thanks for clarification, I was checking from CQE_RX_COALESCED_4
perspective.

> The fatal CQE error means the "default" case. On 'CQE_RX_TRUNCATED' the code can recover when all CQEs are read. But on "default", it's a dead loop.
> 

ack.

>>
>>
>>> Signed-off-by: Long Li <longli at microsoft.com>
>>> ---
>>>  drivers/net/mana/rx.c | 18 ++++++++----------
>>>  1 file changed, 8 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/net/mana/rx.c b/drivers/net/mana/rx.c index
>>> cacfd9ae1b..220b372b15 100644
>>> --- a/drivers/net/mana/rx.c
>>> +++ b/drivers/net/mana/rx.c
>>> @@ -416,23 +416,21 @@ mana_rx_burst(void *dpdk_rxq, struct rte_mbuf
>>> **pkts, uint16_t pkts_n)
>>>
>>>  		switch (oob->cqe_hdr.cqe_type) {
>>>  		case CQE_RX_OKAY:
>>> +		case CQE_RX_COALESCED_4:
>>>  			/* Proceed to process mbuf */
>>>  			break;
>>>
>>>  		case CQE_RX_TRUNCATED:
>>> -			DP_LOG(DEBUG, "Drop a truncated packet");
>>> +		default:
>>> +			DP_LOG(ERR, "RX CQE type %d client %d vendor %d",
>>> +			       oob->cqe_hdr.cqe_type, oob->cqe_hdr.client_type,
>>> +			       oob->cqe_hdr.vendor_err);
>>> +
>>>  			rxq->stats.errors++;
>>>  			rte_pktmbuf_free(mbuf);
>>> -			goto drop;
>>> -
>>> -		case CQE_RX_COALESCED_4:
>>> -			/* Proceed to process mbuf */
>>> -			break;
>>>
>>> -		default:
>>> -			DP_LOG(ERR, "Unknown RX CQE type %d",
>>> -			       oob->cqe_hdr.cqe_type);
>>> -			continue;
>>> +			i++;
>>> +			goto drop;
>>>  		}
>>>
>>>  		DP_LOG(DEBUG, "mana_rx_comp_oob type %d rxq %p",
>