From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752786AbbG3N7v (ORCPT ); Thu, 30 Jul 2015 09:59:51 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:33771 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751263AbbG3N7t convert rfc822-to-8bit (ORCPT ); Thu, 30 Jul 2015 09:59:49 -0400 From: Michal Nazarewicz To: Feng Tang , Andrew Morton , Kyungmin Park , Marek Szyprowski , Joonsoo Kim , linux-kernel@vger.kernel.org Cc: Feng Tang Subject: Re: [PATCH] CMA: Don't return a valid cma for non-cma dev In-Reply-To: <1438223828-26140-1-git-send-email-feng.tang@intel.com> Organization: http://mina86.com/ References: <1438223828-26140-1-git-send-email-feng.tang@intel.com> User-Agent: Notmuch/0.19+53~g2e63a09 (http://notmuchmail.org) Emacs/25.0.50.1 (x86_64-unknown-linux-gnu) X-Face: PbkBB1w#)bOqd`iCe"Ds{e+!C7`pkC9a|f)Qo^BMQvy\q5x3?vDQJeN(DS?|-^$uMti[3D*#^_Ts"pU$jBQLq~Ud6iNwAw_r_o_4]|JO?]}P_}Nc&"p#D(ZgUb4uCNPe7~a[DbPG0T~!&c.y$Ur,=N4RT>]dNpd;KFrfMCylc}gc??'U2j,!8%xdD Face: 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 X-PGP: 50751FF4 X-PGP-FP: AC1F 5F5C D418 88F8 CC84 5858 2060 4012 5075 1FF4 X-Hashcash: 1:20:150730:iamjoonsoo.kim@lge.com::DeSJC/POs413HDHT:0000000000000000000000000000000000000000Mdv X-Hashcash: 1:20:150730:linux-kernel@vger.kernel.org::knWyTBQi53dN3fH/:0000000000000000000000000000000001XM3 X-Hashcash: 1:20:150730:kyungmin.park@samsung.com::/Qm1mVuJ4YWNrU7k:0000000000000000000000000000000000001evP X-Hashcash: 1:20:150730:akpm@linux-foundation.org::VKHE5oNlqo1GH3Wa:0000000000000000000000000000000000001gPF X-Hashcash: 1:20:150730:feng.tang@intel.com::pOotCVMVmr74RiiU:0000000000000000000000000000000000000000003Lp2 X-Hashcash: 1:20:150730:feng.tang@intel.com::vASsKVEF46H5Lo4W:0000000000000000000000000000000000000000004Gk3 X-Hashcash: 1:20:150730:m.szyprowski@samsung.com::+HJgPr1f3f8tQg17:00000000000000000000000000000000000004n3l Date: Thu, 30 Jul 2015 15:59:45 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 30 2015, Feng Tang wrote: > When system(one x86 soc) boot, we saw many normal dma allocation requests > goes to cma area. The call chain is > dma_generic_alloc_coherent > dma_alloc_from_contiguous -- arch/x86/kernel/pci-dma.c > cma_alloc(dev_get_cma_area(dev), count, align) > > Current dev_get_cma_area() will return a valid "cma" anyway. Then all > these requests will be taken as valid cma request, and get pages from > cma area, which has 2 problems: > 1. make the cma area fragmented > 2. confuse the cma reservation, usually cma memory size is set according > to the expectation of system scenario, these unexpected requests > will affect the designed cma usage. > > So this patch will enforce the judgement, and only return valid "cma" > for real cma user, thus make normal user like IO device driver not > abuse cma reserved region. Just don’t set dma_contiguous_default_area. This patch defeats the purpose of a *default* area. > Signed-off-by: Feng Tang > --- > include/linux/dma-contiguous.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h > index 569bbd0..d6ccc19 100644 > --- a/include/linux/dma-contiguous.h > +++ b/include/linux/dma-contiguous.h > @@ -66,7 +66,8 @@ static inline struct cma *dev_get_cma_area(struct device *dev) > { > if (dev && dev->cma_area) > return dev->cma_area; > - return dma_contiguous_default_area; > + else > + return NULL; > } > > static inline void dev_set_cma_area(struct device *dev, struct cma *cma) > -- > 1.7.9.5 > -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +------ooO--(_)--Ooo--