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=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 9E426C49361 for ; Thu, 17 Jun 2021 18:56:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74F1E613E1 for ; Thu, 17 Jun 2021 18:56:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232253AbhFQS7A (ORCPT ); Thu, 17 Jun 2021 14:59:00 -0400 Received: from foss.arm.com ([217.140.110.172]:58570 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbhFQS67 (ORCPT ); Thu, 17 Jun 2021 14:58:59 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 73B131424; Thu, 17 Jun 2021 11:56:51 -0700 (PDT) Received: from [10.57.9.136] (unknown [10.57.9.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A93833F694; Thu, 17 Jun 2021 11:56:49 -0700 (PDT) Subject: Re: [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict() To: Lu Baolu , John Garry , joro@8bytes.org, will@kernel.org, dwmw2@infradead.org, corbet@lwn.net Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxarm@huawei.com, thunder.leizhen@huawei.com, chenxiang66@hisilicon.com, linux-doc@vger.kernel.org References: <1623841437-211832-1-git-send-email-john.garry@huawei.com> <1623841437-211832-7-git-send-email-john.garry@huawei.com> From: Robin Murphy Message-ID: <7d0fb0e2-4671-16db-6963-b0493d7a549b@arm.com> Date: Thu, 17 Jun 2021 19:56:44 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-06-17 08:36, Lu Baolu wrote: > On 6/16/21 7:03 PM, John Garry wrote: >> We only ever now set strict mode enabled in iommu_set_dma_strict(), so >> just remove the argument. >> >> Signed-off-by: John Garry >> Reviewed-by: Robin Murphy >> --- >>   drivers/iommu/amd/init.c    | 2 +- >>   drivers/iommu/intel/iommu.c | 6 +++--- >>   drivers/iommu/iommu.c       | 5 ++--- >>   include/linux/iommu.h       | 2 +- >>   4 files changed, 7 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c >> index fb3618af643b..7bc460052678 100644 >> --- a/drivers/iommu/amd/init.c >> +++ b/drivers/iommu/amd/init.c >> @@ -3099,7 +3099,7 @@ static int __init parse_amd_iommu_options(char >> *str) >>       for (; *str; ++str) { >>           if (strncmp(str, "fullflush", 9) == 0) { >>               pr_warn("amd_iommu=fullflush deprecated; use >> iommu.strict instead\n"); >> -            iommu_set_dma_strict(true); >> +            iommu_set_dma_strict(); >>           } >>           if (strncmp(str, "force_enable", 12) == 0) >>               amd_iommu_force_enable = true; >> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c >> index d586990fa751..0618c35cfb51 100644 >> --- a/drivers/iommu/intel/iommu.c >> +++ b/drivers/iommu/intel/iommu.c >> @@ -454,7 +454,7 @@ static int __init intel_iommu_setup(char *str) >>               iommu_dma_forcedac = true; >>           } else if (!strncmp(str, "strict", 6)) { >>               pr_warn("intel_iommu=strict deprecated; use iommu.strict >> instead\n"); >> -            iommu_set_dma_strict(true); >> +            iommu_set_dma_strict(); >>           } else if (!strncmp(str, "sp_off", 6)) { >>               pr_info("Disable supported super page\n"); >>               intel_iommu_superpage = 0; >> @@ -4382,7 +4382,7 @@ int __init intel_iommu_init(void) >>            */ >>           if (cap_caching_mode(iommu->cap)) { >>               pr_warn("IOMMU batching disallowed due to >> virtualization\n"); >> -            iommu_set_dma_strict(true); >> +            iommu_set_dma_strict(); >>           } >>           iommu_device_sysfs_add(&iommu->iommu, NULL, >>                          intel_iommu_groups, >> @@ -5699,7 +5699,7 @@ static void quirk_calpella_no_shadow_gtt(struct >> pci_dev *dev) >>       } else if (dmar_map_gfx) { >>           /* we have to ensure the gfx device is idle before we flush */ >>           pci_info(dev, "Disabling batched IOTLB flush on Ironlake\n"); >> -        iommu_set_dma_strict(true); >> +        iommu_set_dma_strict(); >>       } >>   } >>   DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0040, >> quirk_calpella_no_shadow_gtt); >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 60b1ec42e73b..ff221d3ddcbc 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str) >>   } >>   early_param("iommu.strict", iommu_dma_setup); >> -void iommu_set_dma_strict(bool strict) >> +void iommu_set_dma_strict(void) >>   { >> -    if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT)) >> -        iommu_dma_strict = strict; >> +    iommu_dma_strict = true; > > Sorry, I still can't get how iommu.strict kernel option works. > > static int __init iommu_dma_setup(char *str) > { >         int ret = kstrtobool(str, &iommu_dma_strict); Note that this is the bit that does the real work - if the argument parses OK then iommu_dma_strict is reassigned with the appropriate value. The iommu_cmd_line stuff is a bit of additional bookkeeping, basically just so we can see whether default values have been overridden. Robin. > >         if (!ret) >                 iommu_cmd_line |= IOMMU_CMD_LINE_STRICT; >         return ret; > } > early_param("iommu.strict", iommu_dma_setup); > > The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere. Hence, > I am wondering how could it work? A bug or I missed anything? > > Best regards, > baolu > >>   } >>   bool iommu_get_dma_strict(struct iommu_domain *domain) >> diff --git a/include/linux/iommu.h b/include/linux/iommu.h >> index 32d448050bf7..754f67d6dd90 100644 >> --- a/include/linux/iommu.h >> +++ b/include/linux/iommu.h >> @@ -476,7 +476,7 @@ int iommu_enable_nesting(struct iommu_domain >> *domain); >>   int iommu_set_pgtable_quirks(struct iommu_domain *domain, >>           unsigned long quirks); >> -void iommu_set_dma_strict(bool val); >> +void iommu_set_dma_strict(void); >>   bool iommu_get_dma_strict(struct iommu_domain *domain); >>   extern int report_iommu_fault(struct iommu_domain *domain, struct >> device *dev, >>