From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CA67C43381 for ; Thu, 28 Mar 2019 06:19:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CEA320811 for ; Thu, 28 Mar 2019 06:19:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726287AbfC1GS7 (ORCPT ); Thu, 28 Mar 2019 02:18:59 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:41040 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725813AbfC1GS6 (ORCPT ); Thu, 28 Mar 2019 02:18:58 -0400 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 80E7F37A6EFC8D49742D; Thu, 28 Mar 2019 14:18:56 +0800 (CST) Received: from [127.0.0.1] (10.177.23.164) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.408.0; Thu, 28 Mar 2019 14:18:49 +0800 Subject: Re: [PATCH v2 1/1] iommu: Add config option to set lazy mode as default To: Robin Murphy , Jean-Philippe Brucker , John Garry , "Will Deacon" , Joerg Roedel , iommu , linux-kernel References: <20190327150030.11112-1-thunder.leizhen@huawei.com> CC: Hanjun Guo From: "Leizhen (ThunderTown)" Message-ID: <5C9C6748.8050103@huawei.com> Date: Thu, 28 Mar 2019 14:18:48 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/3/28 3:18, Robin Murphy wrote: > On 27/03/2019 15:00, Zhen Lei wrote: >> This allows the default behaviour to be controlled by a kernel config >> option instead of changing the command line for the kernel to include >> "iommu.strict=0" on ARM64 where this is desired. >> >> This is similar to CONFIG_IOMMU_DEFAULT_PASSTHROUGH. >> >> Note: At present, intel_iommu, amd_iommu and s390_iommu use lazy mode as >> default, so there is no need to add code for them. > > That seems a bit self-contradictory - if there's a real need for TLB flush behaviour to be statically configurable and not command-line-based then why should users of other architectures be exempt? Yes，you're right. I will make this configuration to be effective for other architectures. BTW, can you give some opinion about below patches? https://patchwork.kernel.org/patch/10857601/ > >> Signed-off-by: Zhen Lei >> --- >> drivers/iommu/Kconfig | 14 ++++++++++++++ >> drivers/iommu/iommu.c | 5 +++++ >> 2 files changed, 19 insertions(+) >> >> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig >> index 6f07f3b21816c64..5daa110d0e83a07 100644 >> --- a/drivers/iommu/Kconfig >> +++ b/drivers/iommu/Kconfig >> @@ -85,6 +85,20 @@ config IOMMU_DEFAULT_PASSTHROUGH >> >> If unsure, say N here. >> >> +config IOMMU_DMA_DEFAULT_LAZY_MODE >> + bool "IOMMU DMA use lazy mode to flush IOTLB and free IOVA" >> + depends on IOMMU_API >> + 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. Removing the need to pass in kernel parameters through >> + command line. For example, iommu.strict=0 on ARM64. If this is >> + enabled, you can still disable with kernel parameters, such as >> + iommu.strict=1 depending on the architecture. >> + >> + If unsure, say N here. >> + >> config OF_IOMMU >> def_bool y >> depends on OF && IOMMU_API >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 33a982e33716369..5acb98e79b5b32d 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -43,7 +43,12 @@ >> #else >> static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA; >> #endif >> + >> +#ifdef CONFIG_IOMMU_DMA_DEFAULT_LAZY_MODE >> +static bool iommu_dma_strict __read_mostly; >> +#else >> static bool iommu_dma_strict __read_mostly = true; >> +#endif > > For a straightforward boolean, you can simply do: > > static bool foo = IS_ENABLED(CONFIG_FOO); > > but that said, I'm still not particularly convinced that there are a significant number of users in a position to build and install a custom kernel but not edit /etc/default/grub, and who really value the combination of less performance than passthrough with less isolation than strict. > > It's also not necessarily obvious to the user how this interacts with IOMMU_DEFAULT_PASSTHROUGH, so if we really do go down this route, maybe it would be better to refactor the whole lot into a single selection of something like IOMMU_DEFAULT_MODE anyway. > > Robin. > >> >> struct iommu_callback_data { >> const struct iommu_ops *ops; >> -- >> 1.8.3 >> >> > > . > -- Thanks! BestRegards