From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] net: mvpp2: Prevent userspace from changing TX
 affinities
Date: Wed, 08 Nov 2017 10:31:56 +0900 (KST)
Message-ID: <20171108.103156.136116035076396821.davem@davemloft.net>
References: <20171104123347.20540-1-marc.zyngier@arm.com>
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Cc: thomas.petazzoni@free-electrons.com,
        antoine.tenart@free-electrons.com, netdev@vger.kernel.org,
        stable@vger.kernel.org
To: marc.zyngier@arm.com
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From: Marc Zyngier <marc.zyngier@arm.com>
Date: Sat,  4 Nov 2017 12:33:47 +0000

> The mvpp2 driver can't cope at all with the TX affinities being
> changed from userspace, and spit an endless stream of
> 
> [   91.779920] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> [   91.779930] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> [   91.780402] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> [   91.780406] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> [   91.780415] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> [   91.780418] mvpp2 f4000000.ethernet eth2: wrong cpu on the end of Tx processing
> 
> rendering the box completely useless (I've measured around 600k
> interrupts/s on a 8040 box) once irqbalance kicks in and start
> doing its job.
> 
> Obviously, the driver was never designed with this in mind. So let's
> work around the problem by preventing userspace from interacting
> with these interrupts altogether.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Applied and queued up for -stable, thanks.