Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933101AbbD1D0n (ORCPT ); Mon, 27 Apr 2015 23:26:43 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:35511 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932281AbbD1D0k (ORCPT ); Mon, 27 Apr 2015 23:26:40 -0400 Date: Mon, 27 Apr 2015 20:26:37 -0700 From: Benjamin Poirier To: Ido Shamay Cc: Amir Vadai , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mlx4: Fix tx ring affinity_mask creation Message-ID: <20150428032637.GA6169@f1.synalogic.ca> References: <1428683240-22879-1-git-send-email-bpoirier@suse.de> <552A18A8.1040109@dev.mellanox.co.il> <20150414002256.GA22775@f1.synalogic.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150414002256.GA22775@f1.synalogic.ca> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4207 Lines: 90 On 2015/04/13 17:22, Benjamin Poirier wrote: > On 2015/04/12 10:03, Ido Shamay wrote: > > Hi Benjamin, > > > > On 4/10/2015 7:27 PM, Benjamin Poirier wrote: > > >By default, the number of tx queues is limited by the number of online cpus in > > >mlx4_en_get_profile(). However, this limit no longer holds after the ethtool > > >.set_channels method has been called. In that situation, the driver may access > > >invalid bits of certain cpumask variables when queue_index > nr_cpu_ids. > > > > I must say I don't see the above issue with the current code. > > Whatever is the modified value of priv->num_tx_rings_p_up, it will set XPS > > only on queues which have > > been set with CPU affinity mask (no access to invalid bits). > > The problem is not with the call to netif_set_xps_queue() it is with the > calls to cpu_online() and cpumask_set_cpu(). > > For example, if the user calls `ethtool -L ethX tx 32`, queue_index in > mlx4_en_create_tx_ring() can be up to 255. Depending on CONFIG_NR_CPUS > and CONFIG_CPUMASK_OFFSTACK this may result in calls to cpu_online() and > cpumask_set_cpu() with cpu >= nr_cpumask_bits which is an invalid usage > of the cpumask api. The driver will potentially read or write beyond the > end of the bitmap. With CONFIG_CPUMASK_OFFSTACK=y and > CONFIG_DEBUG_PER_CPU_MAPS=y, the aforementioned ethtool call on a system > with <32 cpus triggers the warning in cpumask_check(). > Mellanox, can you please ack the patch as submitted, or clarify what changes you'd like to see given my reply above, or submit a fix of your own for this problem Thanks, -Benjamin > > > > It's true that when priv->num_tx_rings_p_up > nr_cpus. not all queues will > > be set with XPS. > > This is because the code tries to preserve 1:1 mapping of queues to cores, > > to avoid a double mapping > > of queues to cores. > > I guess it's ok to break the 1:1 mapping in this condition, but the commit > > message should say that instead > > of invalid bits. Please fix me if I'm wrong. > > > > >Signed-off-by: Benjamin Poirier > > >--- > > > drivers/net/ethernet/mellanox/mlx4/en_tx.c | 8 +++++--- > > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > > >diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c > > >index 55f9f5c..8c234ec 100644 > > >--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c > > >+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c > > >@@ -143,8 +143,10 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv, > > > ring->hwtstamp_tx_type = priv->hwtstamp_config.tx_type; > > > ring->queue_index = queue_index; > > >- if (queue_index < priv->num_tx_rings_p_up && cpu_online(queue_index)) > > >- cpumask_set_cpu(queue_index, &ring->affinity_mask); > > >+ if (queue_index < priv->num_tx_rings_p_up) > > >+ cpumask_set_cpu_local_first(queue_index, > > >+ priv->mdev->dev->numa_node, > > >+ &ring->affinity_mask); > > Moving from cpumask_set_cpu to cpumask_set_cpu_local_first is great, but > > should come in a different commit, since > > the behavior of the XPS is changed here (xps_cpus[tx_ring[queue_index]] != > > queue_index from now). > > Commit should state of this behavior change. > > Thanks a lot Benjamin. > > > *pring = ring; > > > return 0; > > >@@ -213,7 +215,7 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv, > > > err = mlx4_qp_to_ready(mdev->dev, &ring->wqres.mtt, &ring->context, > > > &ring->qp, &ring->qp_state); > > >- if (!user_prio && cpu_online(ring->queue_index)) > > >+ if (!cpumask_empty(&ring->affinity_mask)) > > > netif_set_xps_queue(priv->dev, &ring->affinity_mask, > > > ring->queue_index); > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/