On 2019/5/31 18:42, John Garry wrote: > >>>> -config IOMMU_DEFAULT_PASSTHROUGH >>>> - bool "IOMMU passthrough by default" >>>> +choice >>>> + prompt "IOMMU default 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 >>> >>> As before: >>> /s/chose/chosen/, /s/allows IOMMU/allows an IOMMU/ >> I'm sorry that the previous version was not modified. >> >>> >>>> + override the default DMA mode of each ARCHs, removing the need to >>> >>> Again, as before: >>> ARCHs should be singular >> OK >> >>> >>>> + pass in kernel parameters through command line. You can still use >>>> + 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 >>>> + translation. 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. >>> >>> why no advisory on how to set if unsure? >> Because the LAZY and STRICT have their own advantages and disadvantages. >> >> Should I say: If unsure, keep the default。 > > Maybe. So you could put this in the help for the choice, * above, and remove the advisory on IOMMU_DEFAULT_PASSTHROUGH. OK, I'll revise it according to this idea in v9. > > However the maintainer may have a different view. > > Thanks, > John > >> >>> >>>> + >>>> +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 >>>> + high performace scenarios. >>> >>> and here? > > > . >
