From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753169AbeDRQGB (ORCPT ); Wed, 18 Apr 2018 12:06:01 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33095 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753126AbeDRQF5 (ORCPT ); Wed, 18 Apr 2018 12:05:57 -0400 X-Google-Smtp-Source: AIpwx48oxxPAjoqfOgl7NqVPy4WU6OeC96hZFglAwh3W42O8JRZkPKoP0zxnnZlMRsv02ZB7+hjzZg== Subject: Re: [PATCH] net: don't use kvzalloc for DMA memory To: Mikulas Patocka , "David S. Miller" , Eric Dumazet Cc: Joby Poriyath , Ben Hutchings , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: From: Eric Dumazet Message-ID: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> Date: Wed, 18 Apr 2018 09:05:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.