From: Lu Baolu <baolu.lu@linux.intel.com>
To: Robin Murphy <robin.murphy@arm.com>, joro@8bytes.org, will@kernel.org
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
Date: Fri, 30 Jul 2021 14:10:48 +0800 [thread overview]
Message-ID: <2c714d77-1852-fe0f-7dcf-aabe09726619@linux.intel.com> (raw)
In-Reply-To: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com>
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 <joro@8bytes.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> 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 <baolu.lu@linux.intel.com>
Best regards,
baolu
next prev parent reply other threads:[~2021-07-30 6:13 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-28 15:58 [PATCH v2 00/24] iommu: Refactor DMA domain strictness Robin Murphy
2021-07-28 15:58 ` [PATCH v2 01/24] iommu: Pull IOVA cookie management into the core Robin Murphy
2021-07-30 6:06 ` Lu Baolu
2021-07-30 9:32 ` Jean-Philippe Brucker
2021-07-28 15:58 ` [PATCH v2 02/24] iommu/amd: Drop IOVA cookie management Robin Murphy
2021-07-28 15:58 ` [PATCH v2 03/24] iommu/arm-smmu: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 04/24] iommu/vt-d: " Robin Murphy
2021-07-30 6:07 ` Lu Baolu
2021-07-28 15:58 ` [PATCH v2 05/24] iommu/exynos: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 06/24] iommu/ipmmu-vmsa: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 07/24] iommu/mtk: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 08/24] iommu/rockchip: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 09/24] iommu/sprd: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 10/24] iommu/sun50i: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 11/24] iommu/virtio: " Robin Murphy
2021-07-30 9:20 ` Jean-Philippe Brucker
2021-07-28 15:58 ` [PATCH v2 12/24] iommu/dma: Unexport " Robin Murphy
2021-07-30 6:07 ` Lu Baolu
2021-07-30 9:21 ` Jean-Philippe Brucker
2021-07-28 15:58 ` [PATCH v2 13/24] iommu/dma: Remove redundant "!dev" checks Robin Murphy
2021-07-30 6:08 ` Lu Baolu
2021-07-28 15:58 ` [PATCH v2 14/24] iommu: Introduce explicit type for non-strict DMA domains Robin Murphy
2021-07-30 6:08 ` Lu Baolu
2021-07-30 9:23 ` Jean-Philippe Brucker
2021-07-28 15:58 ` [PATCH v2 15/24] iommu/amd: Prepare for multiple DMA domain types Robin Murphy
2021-07-28 15:58 ` [PATCH v2 16/24] iommu/arm-smmu: " Robin Murphy
2021-07-28 15:58 ` [PATCH v2 17/24] iommu/vt-d: " Robin Murphy
2021-07-30 6:09 ` Lu Baolu
2021-07-28 15:58 ` [PATCH v2 18/24] iommu: Express DMA strictness via the domain type Robin Murphy
2021-07-29 7:13 ` Lu Baolu
2021-07-29 9:36 ` Robin Murphy
2021-07-29 12:42 ` Lu Baolu
2021-07-30 6:09 ` Lu Baolu
2021-07-28 15:58 ` [PATCH v2 19/24] iommu: Expose DMA domain strictness via sysfs Robin Murphy
2021-07-30 6:10 ` Lu Baolu
2021-07-30 9:28 ` Jean-Philippe Brucker
2021-07-30 10:20 ` John Garry
2021-07-28 15:58 ` [PATCH v2 20/24] iommu: Merge strictness and domain type configs Robin Murphy
2021-07-30 6:10 ` Lu Baolu [this message]
2021-07-30 9:29 ` Jean-Philippe Brucker
2021-07-30 9:33 ` John Garry
2021-07-28 15:58 ` [PATCH v2 21/24] iommu/dma: Factor out flush queue init Robin Murphy
2021-07-30 6:11 ` Lu Baolu
2021-07-30 9:20 ` John Garry
2021-07-28 15:58 ` [PATCH v2 22/24] iommu: Allow enabling non-strict mode dynamically Robin Murphy
2021-07-30 6:11 ` Lu Baolu
2021-07-30 9:24 ` John Garry
2021-07-28 15:58 ` [PATCH v2 23/24] iommu/arm-smmu: Allow non-strict in pgtable_quirks interface Robin Murphy
2021-08-02 13:04 ` Will Deacon
2021-08-02 14:15 ` Robin Murphy
2021-08-03 10:36 ` Will Deacon
2021-08-03 12:13 ` Robin Murphy
2021-08-03 12:35 ` Will Deacon
2021-07-28 15:58 ` [PATCH v2 24/24] iommu: Only log strictness for DMA domains Robin Murphy
2021-07-29 9:04 ` John Garry
2021-07-30 6:12 ` Lu Baolu
2021-07-29 2:55 ` [PATCH v2 00/24] iommu: Refactor DMA domain strictness chenxiang (M)
2021-07-29 10:59 ` Robin Murphy
2021-07-30 1:21 ` chenxiang (M)
2021-07-29 15:04 ` Heiko Stübner
2021-07-29 15:43 ` Robin Murphy
2021-07-29 15:53 ` Heiko Stübner
2021-07-29 16:29 ` Robin Murphy
2021-07-29 22:33 ` Doug Anderson
2021-07-30 0:06 ` Doug Anderson
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