[PATCH] net: mvpp2: Prevent userspace from changing TX affinities

[PATCH] net: mvpp2: Prevent userspace from changing TX affinities

[Marc Zyngier]

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>
---
 drivers/net/ethernet/marvell/mvpp2.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvpp2.c b/drivers/net/ethernet/marvell/mvpp2.c
index a37af5813f33..fcf9ba5eb8d1 100644
--- a/drivers/net/ethernet/marvell/mvpp2.c
+++ b/drivers/net/ethernet/marvell/mvpp2.c
@@ -6747,6 +6747,9 @@ static int mvpp2_irqs_init(struct mvpp2_port *port)
 	for (i = 0; i < port->nqvecs; i++) {
 		struct mvpp2_queue_vector *qv = port->qvecs + i;
 
+		if (qv->type == MVPP2_QUEUE_VECTOR_PRIVATE)
+			irq_set_status_flags(qv->irq, IRQ_NO_BALANCING);
+
 		err = request_irq(qv->irq, mvpp2_isr, 0, port->dev->name, qv);
 		if (err)
 			goto err;
@@ -6776,6 +6779,7 @@ static void mvpp2_irqs_deinit(struct mvpp2_port *port)
 		struct mvpp2_queue_vector *qv = port->qvecs + i;
 
 		irq_set_affinity_hint(qv->irq, NULL);
+		irq_clear_status_flags(qv->irq, IRQ_NO_BALANCING);
 		free_irq(qv->irq, qv);
 	}
 }
-- 
2.11.0

Re: [PATCH] net: mvpp2: Prevent userspace from changing TX affinities

[David Miller]

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.