On 2021-06-15 08:26, Lu Baolu wrote:
Hi John,

On 6/14/21 4:03 PM, John Garry wrote:
On 12/06/2021 03:14, Lu Baolu wrote:
On 2021/6/11 20:20, John Garry wrote:
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 2a71347611d4..4467353f981b 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -94,6 +94,7 @@ choice
      prompt "IOMMU default DMA mode"
      depends on IOMMU_DMA
+    default IOMMU_DEFAULT_LAZY if INTEL_IOMMU
      default IOMMU_DEFAULT_STRICT

If two default values are different. Which one will be overridden?

If I understand your question correctly, I think you are asking if both are set:
CONFIG_IOMMU_DEFAULT_LAZY=y
CONFIG_IOMMU_DEFAULT_STRICT=y

If this happens, then make defconfig complains about both being set, and selects the 2nd, whatever that is.

On x86, Intel or AMD, this will be

     prompt "IOMMU default DMA mode"
       depends on IOMMU_DMA
       default IOMMU_DEFAULT_LAZY
       default IOMMU_DEFAULT_STRICT

which will be default, LAZY or STRICT? Will it cause complains?

See Documentation/kbuild/kconfig-language.rst:

  A config option can have any number of default values. If multiple
  default values are visible, only the first defined one is active.


Robin.
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