linux-kernel - Re: [PATCH net] net: mvpp2: prs: Don't override the sign bit in SRAM parser shift

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Message-ID: <64727f68-866b-b2eb-38c9-5670efe68aaf@cogentembedded.com>
Date:   Thu, 20 Jun 2019 11:58:18 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>,
        davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        thomas.petazzoni@...tlin.com, gregory.clement@...tlin.com,
        nadavh@...vell.com, stefanc@...vell.com, mw@...ihalf.com,
        Alan Winkowski <walan@...vell.com>
Subject: Re: [PATCH net] net: mvpp2: prs: Don't override the sign bit in SRAM
 parser shift

On 19.06.2019 17:54, Maxime Chevallier wrote:

> The Header Parser allows identifying various fields in the packet
> headers, used for for various kind of filtering and classification

    One "for" is enough. :-)

> steps.
> 
> This is a re-entrant process, where the offset in the packet header
> depends on the previous lookup results. This offset is represented in
> the SRAM results of the TCAM, as a shift to be operated.
> 
> This shift can be negative in some cases, such as in IPv6 parsing.
> 
> This commit prevents overriding the sign bit when setting the shift
> value, which could cause instabilities when parsing IPv6 flows.
> 
> Fixes: 3f518509dedc ("ethernet: Add new driver for Marvell Armada 375 network unit")
> Suggested-by: Alan Winkowski <walan@...vell.com>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
[...]

MBR, Sergei