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Fri, 30 Jul 2021 06:13:31 +0000 Received: from mga11.intel.com ([192.55.52.93]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9Lle-007PGP-8c for linux-arm-kernel@lists.infradead.org; Fri, 30 Jul 2021 06:13:12 +0000 X-IronPort-AV: E=McAfee;i="6200,9189,10060"; a="209926201" X-IronPort-AV: E=Sophos;i="5.84,281,1620716400"; d="scan'208";a="209926201" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2021 23:13:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.84,281,1620716400"; d="scan'208";a="465345218" Received: from allen-box.sh.intel.com (HELO [10.239.159.118]) ([10.239.159.118]) by orsmga008.jf.intel.com with ESMTP; 29 Jul 2021 23:13:06 -0700 Cc: baolu.lu@linux.intel.com, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suravee.suthikulpanit@amd.com, john.garry@huawei.com, dianders@chromium.org Subject: Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs To: Robin Murphy , joro@8bytes.org, will@kernel.org References: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> From: Lu Baolu Message-ID: <2c714d77-1852-fe0f-7dcf-aabe09726619@linux.intel.com> Date: Fri, 30 Jul 2021 14:10:48 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210729_231310_420226_C19502A2 X-CRM114-Status: GOOD ( 40.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/28/21 11:58 PM, Robin Murphy wrote: > To parallel the sysfs behaviour, merge the new build-time option > for DMA domain strictness into the default domain type choice. > > Suggested-by: Joerg Roedel > Signed-off-by: Robin Murphy > --- > drivers/iommu/Kconfig | 80 +++++++++++++++++++++---------------------- > drivers/iommu/iommu.c | 2 +- > 2 files changed, 41 insertions(+), 41 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index c84da8205be7..6e06f876d75a 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS > debug/iommu directory, and then populate a subdirectory with > entries as required. > > -config IOMMU_DEFAULT_PASSTHROUGH > - bool "IOMMU passthrough by default" > - 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. > - > - If unsure, say N here. > - > choice > - prompt "IOMMU default DMA IOTLB invalidation mode" > - depends on IOMMU_DMA > - > - default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU) > - default IOMMU_DEFAULT_STRICT > + prompt "IOMMU default domain type" > + depends on IOMMU_API > + default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU > + default IOMMU_DEFAULT_DMA_STRICT > help > - This option allows an IOMMU DMA IOTLB invalidation mode to be > - chosen at build time, to override the default mode of each ARCH, > - removing the need to pass in kernel parameters through command line. > - It is still possible to provide common boot params to override this > - config. > + Choose the type of IOMMU domain used to manage DMA API usage by > + device drivers. The options here typically represent different > + levels of tradeoff between robustness/security and performance, > + depending on the IOMMU driver. Not all IOMMUs support all options. > + This choice can be overridden at boot via the command line, and for > + some devices also at runtime via sysfs. > > If unsure, keep the default. > > -config IOMMU_DEFAULT_STRICT > - bool "strict" > +config IOMMU_DEFAULT_DMA_STRICT > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent > + to passing "iommu.passthrough=0 iommu.strict=1" on the command line. > > -config IOMMU_DEFAULT_LAZY > - bool "lazy" > + Untrusted devices always use this mode, with an additional layer of > + bounce-buffering such that they cannot gain access to any unrelated > + data within a mapped page. > + > +config IOMMU_DEFAULT_DMA_LAZY > + bool "Translated - 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. > + Trusted devices use translation to restrict their access to only > + DMA-mapped pages, but with "lazy" batched TLB invalidation. This > + mode allows higher performance with some IOMMUs due to reduced TLB > + flushing, but at the cost of reduced isolation since devices may be > + able to access memory for some time after it has been unmapped. > + Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the > + command line. > > - The isolation provided in this mode is not as secure as STRICT mode, > - such that a vulnerable time window may be created between the DMA > - unmap and the mappings cached in the IOMMU IOTLB or device TLB > - finally being invalidated, where the device could still access the > - memory which has already been unmapped by the device driver. > - However this mode may provide better performance in high throughput > - scenarios, and is still considerably more secure than passthrough > - mode or no IOMMU. > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > + > +config IOMMU_DEFAULT_PASSTHROUGH > + bool "Passthrough" > + help > + Trusted devices are identity-mapped, giving them unrestricted access > + to memory with minimal performance overhead. Equivalent to passing > + "iommu.passthrough=1" (historically "iommu=pt") on the command line. > + > + If this mode is not supported by the IOMMU driver, the effective > + runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT. > > endchoice > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 5a08e0806cbb..25c1adc1ec67 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -31,7 +31,7 @@ static struct kset *iommu_group_kset; > static DEFINE_IDA(iommu_group_ida); > > static unsigned int iommu_def_domain_type __read_mostly; > -static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); > +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT); > static u32 iommu_cmd_line __read_mostly; > > struct iommu_group { > Reviewed-by: Lu Baolu Best regards, baolu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel