Re: QEMU SMMUv3 stage 2 translation

[Auger Eric]

Hi Shashi,

[ fixing my email address ]

On 5/13/21 4:25 PM, Shashi Mallela wrote:
> Hi,
> 
> Since the current SMMUv3 qemu implementation only supports stage 1
> translation,wanted to understand if the implementation could be extended
> to stage 2 translation support and if yes what is the overall scope
> involved.This is required for sbsa-ref platforms.

Yes I think this is feasible. This would require some additionnal
decoding in the STE and also adapt the page table decoding to stage2
according to AArch64 Virtual Memory System Architecture.

If you proceed I would like this code to be isolated of the stage1
decoding as much as possible to alleviate the maintainance all the more
so the stage1 code is the one likely to be used in production for DPDK
or SVA use cases, let's dream. One of the tricky part is the internal
TLB modeling (cache and IOTLB). In your case you may not need to
implement such internal IOTLB for stage 2 entries as I guess you do not
really target perf and this is the source of lots of bugs/headaches ;-)

Thanks

Eric
> .
> Thanks
> Shashi
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