netdev - Re: [PATCH net-next v3 08/11] virtio_net: Implement IPv4 ethtool flow rules

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Message-ID: <20250925171936-mutt-send-email-mst@kernel.org>
Date: Thu, 25 Sep 2025 17:20:49 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Dan Jurgens <danielj@...dia.com>
Cc: netdev@...r.kernel.org, jasowang@...hat.com, alex.williamson@...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, shameerali.kolothum.thodi@...wei.com,
	jgg@...pe.ca, kevin.tian@...el.com, kuba@...nel.org,
	andrew+netdev@...n.ch, edumazet@...gle.com
Subject: Re: [PATCH net-next v3 08/11] virtio_net: Implement IPv4 ethtool
 flow rules

On Thu, Sep 25, 2025 at 04:13:42PM -0500, Dan Jurgens wrote:
> On 9/25/25 3:53 PM, Michael S. Tsirkin wrote:
> > On Tue, Sep 23, 2025 at 09:19:17AM -0500, Daniel Jurgens wrote:
> >> Add support for IP_USER type rules from ethtool.
> >>
> >> +static
> >> +struct virtio_net_ff_selector *next_selector(struct virtio_net_ff_selector *sel)
> >> +{
> >> +	void *nextsel;
> >> +
> >> +	nextsel = (u8 *)sel + sizeof(struct virtio_net_ff_selector) +
> >> +		  sel->length;
> > 
> > you do not need this variable. and cast to void* looks cleaner imho.
> 
> It's cast to u8* so we do pointer arithmetic in bytes, which is not
> standard C on void*. GCC doesn't mind, but I thing Clang does.
> 
> I saw you had a similar comment on a subsequent too.>

it's a known C standard bug.

kernel does void* math everywhere.

Linus hath spoken on this ;)


> >> +
> >> +	return nextsel;
> >> +}
> >> +
>