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From: Robin Murphy <robin.murphy@arm.com>
To: joro@8bytes.org, will@kernel.org
Cc: iommu@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, suravee.suthikulpanit@amd.com,
	baolu.lu@linux.intel.com, john.garry@huawei.com,
	dianders@chromium.org
Subject: [PATCH v2 20/24] iommu: Merge strictness and domain type configs
Date: Wed, 28 Jul 2021 16:58:41 +0100	[thread overview]
Message-ID: <992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com> (raw)
In-Reply-To: <cover.1627468308.git.robin.murphy@arm.com>

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 {
-- 
2.25.1


  parent reply	other threads:[~2021-07-28 16:00 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 ` Robin Murphy [this message]
2021-07-30  6:10   ` [PATCH v2 20/24] iommu: Merge strictness and domain type configs Lu Baolu
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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