Re: [PATCH v12 3/5] iommu/vt-d: Add support for IOMMU default DMA mode build options

[John Garry]

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.

If neither are set, then IOMMU_DEFAULT_LAZY is set if INTEL_IOMMU is 
set, otherwise IOMMU_DEFAULT_STRICT.

Thanks,
John