Re: Re: [XEN-IOMMU] Proposal of DMA protection/isolationsupport

[tgh <wwwwww4187@sina.com.cn>]

hi
IOMMU, could it be used in KVM ,or not? if it could , what about the 
difference between the usage in xen and the usage in KVM?

Thanks




Ian Pratt 写道:
>> After looking into the grant mapping code (use block device as an
>> example), I got some ideas to share with you and the list.  Please
>> correct me if I missed something. There might be 2 places to trigger
>> iommu mapping:
>>
>> 1) Before submitting io request to generic block layer, block backend
>> driver will invoke GNTTABOPs to map granted remote pages .  However
>> creating iommu mapping only in GNTTABOP not very enough because local
>> pages will also be submitted to block layer and they should also be
>> translated by iommu.
>>
>> 2) When dma layer is invoked to prepare a bus address for native block
>> device driver. It would be better to have a "hypervisor-aware" dma
>> layer
>> which always maps virtual address to bus address via hypercall.
>> __gnttab_dma_map_page() might be a good place to trigger this new
>> hypercall. Both remote and local pages can be mapped by this way.
>>     
>
>
> It's much better to create most mappings in #1 when the operations are
> easily batchable into a single hypercall, and then fill in the missing
> mappings when required at #2.
>
> Since in many situations dom0 does very little IO for itself, this
> should be a significant win, especially for networking.
>
> Ian
>  
>
>
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