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Subject[PATCH v5 2/6] iommu: add build options corresponding to iommu.dma_mode
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First, add build option IOMMU_DEFAULT_{LAZY|STRICT}, so that we have the
opportunity to set {lazy|strict} mode as default at build time. Then put
the three config options in an choice, make people can only choose one of
the three at a time, the same to the boot options iommu.dma_mode.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
Documentation/admin-guide/kernel-parameters.txt | 6 ++--
drivers/iommu/Kconfig | 43 +++++++++++++++++++++----
drivers/iommu/iommu.c | 4 ++-
3 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f7766f8ac8b9084..92d1b3151d003c2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1811,9 +1811,9 @@
1 - Bypass the IOMMU for DMA.
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.

- iommu.dma_mode= Configure default dma mode. if unset, use the value
- of CONFIG_IOMMU_DEFAULT_PASSTHROUGH to determine
- passthrough or not.
+ iommu.dma_mode= Configure default dma mode. if unset, use the build
+ options(such as CONFIG_IOMMU_DEFAULT_PASSTHROUGH) to
+ choose which mode to be used.
Note: For historical reasons, ARM64/S390/PPC/X86 have
their specific options. Currently, only ARM64 support
this boot option, and hope other ARCHs to use this as
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 6f07f3b21816c64..1986f9767da488b 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -74,17 +74,46 @@ config IOMMU_DEBUGFS
debug/iommu directory, and then populate a subdirectory with
entries as required.

-config IOMMU_DEFAULT_PASSTHROUGH
- bool "IOMMU passthrough by default"
+choice
+ prompt "IOMMU dma mode"
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.
+ default IOMMU_DEFAULT_STRICT
+ help
+ This option allows IOMMU dma mode to be chose at build time, to
+ override the default dma mode of each ARCHs, removing the need to
+ pass in kernel parameters through command line. You can still use the
+ generic boot option iommu.dma_mode or ARCHs specific boot options to
+ override this option again.
+
+config IOMMU_DEFAULT_PASSTHROUGH
+ bool "passthrough"
+ help
+ In this mode, the dma access through IOMMU without any addresses
+ transformation. That means, the wrong or illegal dma access can not
+ be caught, no error information will be reported.

If unsure, say N here.

+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.
+
+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.
+
+ This mode is safer than the two above, but it maybe slow in some high
+ performace scenarios.
+
+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 df1ce8e22385b48..f4171bf4b46eaeb 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -39,8 +39,10 @@
static struct kset *iommu_group_kset;
static DEFINE_IDA(iommu_group_ida);

-#ifdef CONFIG_IOMMU_DEFAULT_PASSTHROUGH
+#if defined(CONFIG_IOMMU_DEFAULT_PASSTHROUGH)
#define IOMMU_DEFAULT_DMA_MODE IOMMU_DMA_MODE_PASSTHROUGH
+#elif defined(CONFIG_IOMMU_DEFAULT_LAZY)
+#define IOMMU_DEFAULT_DMA_MODE IOMMU_DMA_MODE_LAZY
#else
#define IOMMU_DEFAULT_DMA_MODE IOMMU_DMA_MODE_STRICT
#endif
--
1.8.3

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