netdev - Re: [PATCH net-next v11 05/12] virtio_net: Query and set flow filter caps

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Message-ID: <b5b414b8-23fb-4e46-9b98-9db2a07940c6@nvidia.com>
Date: Wed, 19 Nov 2025 08:47:28 -0600
From: Dan Jurgens <danielj@...dia.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org, jasowang@...hat.com, pabeni@...hat.com,
 virtualization@...ts.linux.dev, parav@...dia.com, shshitrit@...dia.com,
 yohadt@...dia.com, xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
 jgg@...pe.ca, kevin.tian@...el.com, kuba@...nel.org, andrew+netdev@...n.ch,
 edumazet@...gle.com
Subject: Re: [PATCH net-next v11 05/12] virtio_net: Query and set flow filter
 caps

On 11/19/25 1:53 AM, Michael S. Tsirkin wrote:
> On Tue, Nov 18, 2025 at 08:38:55AM -0600, Daniel Jurgens wrote:
>> +/**
>> + * struct virtio_net_ff_cap_data - Flow filter resource capability limits
>> + * @groups_limit: maximum number of flow filter groups supported by the device
>> + * @classifiers_limit: maximum number of classifiers supported by the device
>> + * @rules_limit: maximum number of rules supported device-wide across all groups
>> + * @rules_per_group_limit: maximum number of rules allowed in a single group
>> + * @last_rule_priority: priority value associated with the lowest-priority rule
>> + * @selectors_per_classifier_limit: maximum selectors allowed in one classifier
>> + *
>> + * The limits are reported by the device and describe resource capacities for
>> + * flow filters.
> 
> This sentence adds nothing of substance.
> Pls don't add fluff like this in comments.
> 
>> Multi-byte fields are little-endian.
> 

Done

> 
> You do not really need to say "Multi-byte fields are little-endian."
> do you? It says __le explicitly. Same applies to all structures.
> 
>> + */
>> +struct virtio_net_ff_cap_data {
>> +	__le32 groups_limit;
>> +	__le32 classifiers_limit;
>> +	__le32 rules_limit;
>> +	__le32 rules_per_group_limit;
>> +	__u8 last_rule_priority;
>> +	__u8 selectors_per_classifier_limit;
>> +};
> 
> so the compiler adds 2 bytes of padding here. The bug is
> in the spec.
> 
> I think this happens to work for people because controllers
> either also added 2 bytes of padding here at the end,
> or they report a shorter structure and
> the spec says commands can be truncated.
> So I think we can just add 2 bytes of padding at the end
> and it will be harmless.
> 
> It is a spec extension, but a minor one.

Done, referenced your spec patch in the change log.

> 
>