From: John Garry <john.garry@huawei.com>
To: <joro@8bytes.org>, <will@kernel.org>, <dwmw2@infradead.org>,
<baolu.lu@linux.intel.com>, <robin.murphy@arm.com>,
<corbet@lwn.net>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxarm@huawei.com, iommu@lists.linux-foundation.org
Subject: [PATCH v14 3/6] iommu: Enhance IOMMU default DMA mode build options
Date: Fri, 18 Jun 2021 19:34:15 +0800 [thread overview]
Message-ID: <1624016058-189713-4-git-send-email-john.garry@huawei.com> (raw)
In-Reply-To: <1624016058-189713-1-git-send-email-john.garry@huawei.com>
From: Zhen Lei <thunder.leizhen@huawei.com>
First, add build options IOMMU_DEFAULT_{LAZY|STRICT}, so that we have the
opportunity to set {lazy|strict} mode as default at build time. Then put
the two config options in an choice, as they are mutually exclusive.
[jpg: Make choice between strict and lazy only (and not passthrough)]
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
.../admin-guide/kernel-parameters.txt | 3 +-
drivers/iommu/Kconfig | 40 +++++++++++++++++++
drivers/iommu/iommu.c | 2 +-
3 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 673952379900..a1b7c8526bb5 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2046,9 +2046,10 @@
throughput at the cost of reduced device isolation.
Will fall back to strict mode if not supported by
the relevant IOMMU driver.
- 1 - Strict mode (default).
+ 1 - Strict mode.
DMA unmap operations invalidate IOMMU hardware TLBs
synchronously.
+ unset - Use value of CONFIG_IOMMU_DEFAULT_{LAZY,STRICT}.
Note: on x86, the default behaviour depends on the
equivalent driver-specific parameters, but a strict
mode explicitly specified by either method takes
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 1f111b399bca..0327a942fdb7 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -90,6 +90,46 @@ config IOMMU_DEFAULT_PASSTHROUGH
If unsure, say N here.
+choice
+ prompt "IOMMU default DMA IOTLB invalidation mode"
+ depends on IOMMU_DMA
+
+ default IOMMU_DEFAULT_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.
+
+ If unsure, keep the default.
+
+config IOMMU_DEFAULT_STRICT
+ bool "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.
+
+config IOMMU_DEFAULT_LAZY
+ bool "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.
+
+ 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.
+
+endchoice
+
config OF_IOMMU
def_bool y
depends on OF && IOMMU_API
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index cf58949cc2f3..60b1ec42e73b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -29,7 +29,7 @@ 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 = true;
+static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT);
static u32 iommu_cmd_line __read_mostly;
struct iommu_group {
--
2.26.2
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-06-18 11:39 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 11:34 [PATCH v14 0/6] iommu: Enhance IOMMU default DMA mode build options John Garry
2021-06-18 11:34 ` [PATCH v14 1/6] iommu: Deprecate Intel and AMD cmdline methods to enable strict mode John Garry
2021-06-18 13:09 ` Lu Baolu
2021-06-18 11:34 ` [PATCH v14 2/6] iommu: Print strict or lazy mode at init time John Garry
2021-06-18 13:10 ` Lu Baolu
2021-06-18 11:34 ` John Garry [this message]
2021-06-18 13:11 ` [PATCH v14 3/6] iommu: Enhance IOMMU default DMA mode build options Lu Baolu
2021-06-18 11:34 ` [PATCH v14 4/6] iommu/vt-d: Add support for " John Garry
2021-06-18 13:12 ` Lu Baolu
2021-06-18 11:34 ` [PATCH v14 5/6] iommu/amd: " John Garry
2021-06-18 11:34 ` [PATCH v14 6/6] iommu: Remove mode argument from iommu_set_dma_strict() John Garry
2021-06-18 13:13 ` Lu Baolu
2021-06-21 5:17 ` Lu Baolu
2021-06-21 8:12 ` John Garry
2021-06-21 10:00 ` Lu Baolu
2021-06-21 10:34 ` John Garry
2021-06-21 11:59 ` Robin Murphy
2021-06-21 12:08 ` John Garry
2021-06-21 14:32 ` Lu Baolu
2021-06-22 22:25 ` Robin Murphy
2021-06-23 7:21 ` Lu Baolu
2021-06-25 16:41 ` [PATCH v14 0/6] iommu: Enhance IOMMU default DMA mode build options John Garry
2021-07-08 9:38 ` joro
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