netdev - Re: [PATCH RFC v2 net-next 4/4] net: ena: Add support to changing tx_push_buf

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Message-ID: <pj41zllek827gc.fsf@u570694869fb251.ant.amazon.com>
Date:   Mon, 6 Mar 2023 13:54:40 +0200
From:   Shay Agroskin <shayagr@...zon.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
        "Woodhouse, David" <dwmw@...zon.com>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        Saeed Bshara <saeedb@...zon.com>,
        "Wilson, Matt" <msw@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        "Bshara, Nafea" <nafea@...zon.com>,
        "Belgazal, Netanel" <netanel@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Dagan, Noam" <ndagan@...zon.com>,
        "Arinzon, David" <darinzon@...zon.com>,
        "Itzko, Shahar" <itzko@...zon.com>,
        "Abboud, Osama" <osamaabb@...zon.com>
Subject: Re: [PATCH RFC v2 net-next 4/4] net: ena: Add support to changing
 tx_push_buf_len


Jakub Kicinski <kuba@...nel.org> writes:

> On Thu, 2 Mar 2023 22:30:45 +0200 Shay Agroskin wrote:
>> @@ -496,11 +509,40 @@ static int ena_set_ringparam(struct 
>> net_device *netdev,
>>  			ENA_MIN_RING_SIZE : ring->rx_pending;
>>  	new_rx_size = rounddown_pow_of_two(new_rx_size);
>>  
>> -	if (new_tx_size == adapter->requested_tx_ring_size &&
>> -	    new_rx_size == adapter->requested_rx_ring_size)
>> +	changed |= new_tx_size != adapter->requested_tx_ring_size 
>> ||
>> +		   new_rx_size != adapter->requested_rx_ring_size;
>> +
>> +	/* This value is ignored if LLQ is not supported */
>> +	new_tx_push_buf_len = 0;
>> +	if (adapter->ena_dev->tx_mem_queue_type == 
>> ENA_ADMIN_PLACEMENT_POLICY_HOST)
>> +		goto no_llq_supported;
>
> Are you rejecting the unsupported config in this case or just 
> ignoring
> it? You need to return an error if user tries to set something 
> the
> device does not support/allow.
>

I'll explicitly set 0s to push buffer in 'get' when LLQ isn't 
supported and return -ENOSUPP if the user
tries to set it when no LLQ is used.

> BTW your use of gotos to skip code is against the kernel coding 
> style.
> gotos are only for complex cases and error handling, you're 
> using them
> to save indentation it seems. Factor the code out to a helper 
> instead,
> or some such.
>

Modified the code to remove the gotos (although I thought they 
were an elegant implementation)

>> +	new_tx_push_buf_len = kernel_ring->tx_push_buf_len;
>> +
>> +	/* support for ENA_LLQ_LARGE_HEADER is tested in the 'get' 
>> command */
>> +	if (new_tx_push_buf_len != ENA_LLQ_HEADER &&
>> +	    new_tx_push_buf_len != ENA_LLQ_LARGE_HEADER) {
>> +		bool large_llq_sup = 
>> adapter->large_llq_header_supported;
>> +		char large_llq_size_str[40];
>> +
>> +		snprintf(large_llq_size_str, 40, ", %lu", 
>> ENA_LLQ_LARGE_HEADER);
>> +
>> +		NL_SET_ERR_MSG_FMT_MOD(extack,
>> +				       "Only [%lu%s] tx push buff 
>> length values are supported",
>> +				       ENA_LLQ_HEADER,
>> +				       large_llq_sup ? 
>> large_llq_size_str : "");
>> +
>> +		return -EINVAL;
>> +	}
>> +
>> +	changed |= new_tx_push_buf_len != 
>> adapter->ena_dev->tx_max_header_size;
>> +
>> +no_llq_supported:
>> +	if (!changed)
>>  		return 0;
>>  
>> -	return ena_update_queue_sizes(adapter, new_tx_size, 
>> new_rx_size);
>> +	return ena_update_queue_params(adapter, new_tx_size, 
>> new_rx_size,
>> +				       new_tx_push_buf_len);