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SubjectRe: [PATCH v10 1/3] iommu: Enhance IOMMU default DMA mode build options
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On 6/3/21 6:58 AM, John Garry wrote:
> 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>
> ---
> drivers/iommu/Kconfig | 34 ++++++++++++++++++++++++++++++++++
> drivers/iommu/iommu.c | 3 ++-
> 2 files changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 1f111b399bca..12ef90256df8 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -90,6 +90,40 @@ config IOMMU_DEFAULT_PASSTHROUGH
>
> If unsure, say N here.
>
> +choice
> + prompt "IOMMU default DMA mode"
> + depends on IOMMU_API
> +
> + default IOMMU_DEFAULT_STRICT
> + help
> + This option allows an IOMMU DMA mode to be chosen at build time, to
> + override the default DMA mode of each ARCH, removing the need to
> + pass in kernel parameters through command line. It is still possible
> + to provide ARCH-specific or common boot options to override this
> + option.
> +
> + If unsure, keep the default.
> +
> +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 slower in some

There don't seem to be two above?

> + high performace scenarios.

performance

> +
> +endchoice


thanks.
--
~Randy

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