netdev - Re: [PATCH net-next v5 14/15] idpf: add ethtool callbacks

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Message-ID: <301ce6ae-f925-a1a5-3be0-06da4ddfafc1@intel.com>
Date: Wed, 23 Aug 2023 11:05:14 -0700
From: "Linga, Pavan Kumar" <pavan.kumar.linga@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>, <davem@...emloft.net>,
	<pabeni@...hat.com>, <edumazet@...gle.com>, <netdev@...r.kernel.org>, "Alan
 Brady" <alan.brady@...el.com>, <emil.s.tantilov@...el.com>,
	<jesse.brandeburg@...el.com>, <sridhar.samudrala@...el.com>,
	<shiraz.saleem@...el.com>, <sindhu.devale@...el.com>, <willemb@...gle.com>,
	<decot@...gle.com>, <andrew@...n.ch>, <leon@...nel.org>, <mst@...hat.com>,
	<simon.horman@...igine.com>, <shannon.nelson@....com>,
	<stephen@...workplumber.org>, Alice Michael <alice.michael@...el.com>, Joshua
 Hay <joshua.a.hay@...el.com>, Phani Burra <phani.r.burra@...el.com>
Subject: Re: [PATCH net-next v5 14/15] idpf: add ethtool callbacks



On 8/21/2023 2:02 PM, Jakub Kicinski wrote:
> On Mon, 21 Aug 2023 13:41:15 -0700 Linga, Pavan Kumar wrote:
>> On 8/18/2023 11:58 AM, Jakub Kicinski wrote:
>>> On Tue, 15 Aug 2023 17:43:04 -0700 Tony Nguyen wrote:
>>>> +static u32 idpf_get_rxfh_indir_size(struct net_device *netdev)
>>>> +{
>>>> +	struct idpf_vport *vport = idpf_netdev_to_vport(netdev);
>>>> +	struct idpf_vport_user_config_data *user_config;
>>>> +
>>>> +	if (!vport)
>>>> +		return -EINVAL;
>>>
>>> defensive programming? how do we have a netdev and no vport?
>>
>> During a hardware reset, the control plane will reinitialize its vport
>> configuration along with the hardware resources which in turn requires
>> the driver to reallocate the vports as well. For this reason the vports
>> will be freed, but the netdev will be preserved.
> 
> HW reset path should take appropriate locks so that the normal control
> path can't be exposed to transient errors.
> 
> User space will 100% not know what to do with a GET reporting EINVAL.
> 

Agreed, looking into using locks to protect such cases.

>>>> +	dev = &vport->adapter->pdev->dev;
>>>> +	if (!(ch->combined_count || (ch->rx_count && ch->tx_count))) {
>>>> +		dev_err(dev, "Please specify at least 1 Rx and 1 Tx channel\n");
>>>
>>> The error msg doesn't seem to fit the second part of the condition.
>>>
>>
>> The negation part is to the complete check which means it takes 0
>> [tx|rx]_count into consideration.
> 
> Ah, missed the negation. In that case I think the check is not needed,
> pretty sure core checks this.
> 

My bad. After taking a closer look, the above check is similar compared 
to that of the core check. Will remove the check as it is redundant.

>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	num_req_tx_q = ch->combined_count + ch->tx_count;
>>>> +	num_req_rx_q = ch->combined_count + ch->rx_count;
>>>> +
>>>> +	dev = &vport->adapter->pdev->dev;
>>>> +	/* It's possible to specify number of queues that exceeds max in a way
>>>> +	 * that stack won't catch for us, this should catch that.
>>>> +	 */
>>>
>>> How, tho?
>>
>> If the user tries to pass the combined along with the txq or rxq values,
>> then it is possbile to cross the max supported values. So the following
>> checks are needed to protect those cases. Core checks the max values for
>> the individual arguments but not the combined + [tx|rx].
> 
> I see, please add something along those lines to the comment.

Sure, will do.

Thanks,
Pavan