From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 986A17D2EF for ; Thu, 30 May 2019 12:20:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727059AbfE3MUr (ORCPT ); Thu, 30 May 2019 08:20:47 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:17628 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726065AbfE3MUr (ORCPT ); Thu, 30 May 2019 08:20:47 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 2BC0084B9352ECE62CBB; Thu, 30 May 2019 20:20:41 +0800 (CST) Received: from [127.0.0.1] (10.202.227.238) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Thu, 30 May 2019 20:20:31 +0800 Subject: Re: [PATCH v8 1/7] iommu: enhance IOMMU default DMA mode build options To: Zhen Lei , Jean-Philippe Brucker , Robin Murphy , "Will Deacon" , Joerg Roedel , Jonathan Corbet , linux-doc , Sebastian Ott , Gerald Schaefer , "Martin Schwidefsky" , Heiko Carstens , Benjamin Herrenschmidt , Paul Mackerras , "Michael Ellerman" , Tony Luck , Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , David Woodhouse , iommu , linux-kernel , linux-s390 , linuxppc-dev , x86 , linux-ia64 References: <20190530034831.4184-1-thunder.leizhen@huawei.com> <20190530034831.4184-2-thunder.leizhen@huawei.com> CC: Hanjun Guo , Linuxarm From: John Garry Message-ID: <645bd526-4eb0-4a36-2dda-023f009247ab@huawei.com> Date: Thu, 30 May 2019 13:20:16 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20190530034831.4184-2-thunder.leizhen@huawei.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.238] X-CFilter-Loop: Reflected Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 30/05/2019 04:48, Zhen Lei wrote: > First, add build option IOMMU_DEFAULT_{LAZY|STRICT}, so that we have the > opportunity to set {lazy|strict} mode as default at build time. Then put > the three config options in an choice, make people can only choose one of > the three at a time. > Since this was not picked up, but modulo (somtimes same) comments below: Reviewed-by: John Garry > Signed-off-by: Zhen Lei > --- > drivers/iommu/Kconfig | 42 +++++++++++++++++++++++++++++++++++------- > drivers/iommu/iommu.c | 3 ++- > 2 files changed, 37 insertions(+), 8 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 83664db5221df02..d6a1a45f80ffbf5 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -75,17 +75,45 @@ config IOMMU_DEBUGFS > debug/iommu directory, and then populate a subdirectory with > entries as required. > > -config IOMMU_DEFAULT_PASSTHROUGH > - bool "IOMMU passthrough by default" > +choice > + prompt "IOMMU default DMA mode" > depends on IOMMU_API > - help > - Enable passthrough by default, removing the need to pass in > - iommu.passthrough=on or iommu=pt through command line. If this > - is enabled, you can still disable with iommu.passthrough=off > - or iommu=nopt depending on the architecture. > + default IOMMU_DEFAULT_STRICT > + help > + This option allows IOMMU DMA mode to be chose at build time, to As before: /s/chose/chosen/, /s/allows IOMMU/allows an IOMMU/ > + override the default DMA mode of each ARCHs, removing the need to Again, as before: ARCHs should be singular > + pass in kernel parameters through command line. You can still use > + ARCHs specific boot options to override this option again. > + > +config IOMMU_DEFAULT_PASSTHROUGH > + bool "passthrough" > + help > + In this mode, the DMA access through IOMMU without any addresses > + translation. That means, the wrong or illegal DMA access can not > + be caught, no error information will be reported. > > If unsure, say N here. > > +config IOMMU_DEFAULT_LAZY > + bool "lazy" > + help > + Support lazy mode, where for every IOMMU DMA unmap operation, the > + flush operation of IOTLB and the free operation of IOVA are deferred. > + They are only guaranteed to be done before the related IOVA will be > + reused. why no advisory on how to set if unsure? > + > +config IOMMU_DEFAULT_STRICT > + bool "strict" > + help > + For every IOMMU DMA unmap operation, the flush operation of IOTLB and > + the free operation of IOVA are guaranteed to be done in the unmap > + function. > + > + This mode is safer than the two above, but it maybe slower in some > + high performace scenarios. and here? > + > +endchoice > + > config OF_IOMMU > def_bool y > depends on OF && IOMMU_API > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 67ee6623f9b2a4d..56bce221285b15f 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -43,7 +43,8 @@ > #else > static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA; > #endif > -static bool iommu_dma_strict __read_mostly = true; > +static bool iommu_dma_strict __read_mostly = > + IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); > > struct iommu_group { > struct kobject kobj; >