linux-kernel - RE: [EXTERNAL] Re: [PATCH net v1 1/2] octeon_ep: avoid compiler and IQ/OQ reordering

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Message-ID:
 <MN6PR18MB54667119674AC692ED7EF978D39FA@MN6PR18MB5466.namprd18.prod.outlook.com>
Date: Fri, 30 Jan 2026 12:58:36 +0000
From: Vimlesh Kumar <vimleshk@...vell.com>
To: Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: Sathesh B Edara <sedara@...vell.com>,
        Shinas Rasheed
	<srasheed@...vell.com>,
        Haseeb Gani <hgani@...vell.com>,
        Veerasenareddy Burru
	<vburru@...vell.com>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Satananda Burla <sburla@...vell.com>,
        Abhijit Ayarekar
	<aayarekar@...vell.com>
Subject: RE: [EXTERNAL] Re: [PATCH net v1 1/2] octeon_ep: avoid compiler and
 IQ/OQ reordering

Hi @'Paolo Abeni',

Is our reply adequate or do we need to make any other changes? 

Regards.

> -----Original Message-----
> From: Vimlesh Kumar
> Sent: Friday, January 9, 2026 7:56 PM
> To: 'Paolo Abeni' <pabeni@...hat.com>; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Cc: Sathesh B Edara <sedara@...vell.com>; Shinas Rasheed
> <srasheed@...vell.com>; Haseeb Gani <hgani@...vell.com>;
> Veerasenareddy Burru <vburru@...vell.com>; Andrew Lunn
> <andrew+netdev@...n.ch>; David S. Miller <davem@...emloft.net>; Eric
> Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>;
> Satananda Burla <sburla@...vell.com>; Abhijit Ayarekar
> <aayarekar@...vell.com>
> Subject: RE: [EXTERNAL] Re: [PATCH net v1 1/2] octeon_ep: avoid compiler
> and IQ/OQ reordering
> 
> 
> 
> > -----Original Message-----
> > From: Paolo Abeni <pabeni@...hat.com>
> > Sent: Monday, December 29, 2025 9:45 PM
> > To: Vimlesh Kumar <vimleshk@...vell.com>; netdev@...r.kernel.org;
> > linux- kernel@...r.kernel.org
> > Cc: Sathesh B Edara <sedara@...vell.com>; Shinas Rasheed
> > <srasheed@...vell.com>; Haseeb Gani <hgani@...vell.com>;
> > Veerasenareddy Burru <vburru@...vell.com>; Andrew Lunn
> > <andrew+netdev@...n.ch>; David S. Miller <davem@...emloft.net>; Eric
> > Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>;
> > Satananda Burla <sburla@...vell.com>; Abhijit Ayarekar
> > <aayarekar@...vell.com>
> > Subject: [EXTERNAL] Re: [PATCH net v1 1/2] octeon_ep: avoid compiler
> > and IQ/OQ reordering On 12/19/25 8:29 AM, Vimlesh Kumar wrote:
> > > Utilize READ_ONCE and WRITE_ONCE APIs for IO queue Tx/Rx variable
> > > access to prevent compiler optimization and reordering.
> > > Additionally, ensure IO queue OUT/IN_CNT registers are flushed by
> > > performing a read-back after writing.
> >
> > Please explain why such _ONCE() annotation are required, and what
> > could be reordered otherwise.
> >
> > I don't think they are needed,
> >
> 
> We use READ_ONCE and WRITE_ONCE APIs in the data path to prevent the
> compiler from optimizing or reordering read/write operations.
> The APIs are used to access RX and TX queue counter fields that are shared
> between the Octeon hardware device and its device driver. These APIs ensure
> that the driver always reads the most current values from the hardware for
> various RX and TX counter fields. Additionally, they prevent the compiler from
> optimizing or reordering read/write operations on these counter fields.
> 
> > /P