From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752107AbeDRQo3 (ORCPT ); Wed, 18 Apr 2018 12:44:29 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750961AbeDRQo1 (ORCPT ); Wed, 18 Apr 2018 12:44:27 -0400 Date: Wed, 18 Apr 2018 12:44:25 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Eric Dumazet cc: "David S. Miller" , Eric Dumazet , Joby Poriyath , Ben Hutchings , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Michael S. Tsirkin" , Jason Wang , virtualization@lists.linux-foundation.org Subject: Re: [PATCH] net: don't use kvzalloc for DMA memory In-Reply-To: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> Message-ID: References: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 18 Apr 2018, Eric Dumazet wrote: > > > On 04/18/2018 07:34 AM, Mikulas Patocka wrote: > > The patch 74d332c13b21 changes alloc_netdev_mqs to use vzalloc if kzalloc > > fails (later patches change it to kvzalloc). > > > > The problem with this is that if the vzalloc function is actually used, > > virtio_net doesn't work (because it expects that the extra memory should > > be accessible with DMA-API and memory allocated with vzalloc isn't). > > > > This patch changes it back to kzalloc and adds a warning if the allocated > > size is too large (the allocation is unreliable in this case). > > > > Signed-off-by: Mikulas Patocka > > Fixes: 74d332c13b21 ("net: extend net_device allocation to vmalloc()") > > > > --- > > net/core/dev.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > Index: linux-2.6/net/core/dev.c > > =================================================================== > > --- linux-2.6.orig/net/core/dev.c 2018-04-16 21:08:36.000000000 +0200 > > +++ linux-2.6/net/core/dev.c 2018-04-18 16:24:43.000000000 +0200 > > @@ -8366,7 +8366,8 @@ struct net_device *alloc_netdev_mqs(int > > /* ensure 32-byte alignment of whole construct */ > > alloc_size += NETDEV_ALIGN - 1; > > > > - p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL); > > + WARN_ON(alloc_size > PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER); > > + p = kzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL); > > if (!p) > > return NULL; > > > > > > Since when a net_device needs to be in DMA zone ??? > > I would rather fix virtio_net, this looks very suspect to me. > > Each virtio_net should probably allocate the exact amount of DMA-memory it wants, > instead of expecting core networking stack to have a huge chunk of DMA-memory for everything. The structure net_device is followed by arbitrary driver-specific data (accessible with the function netdev_priv). And for virtio-net, these driver-specific data must be in DMA memory. Mikulas