Re: [RFC PATCH 00/21] Add SMMUv3 Stage 1 Support for XEN guests

[Julien Grall <julien@xxxxxxx>]

Hi Rahul,

On 01/12/2022 16:02, Rahul Singh wrote:
> This patch series is sent as RFC to get the initial feedback from the
> community. This patch series consists of 21 patches which is a big number for
> the reviewer to review the patches but to understand the feature end-to-end we
> thought of sending this as a big series. Once we will get initial feedback, we
> will divide the series into a small number of patches for review.
From the cover letter, it is not clear to me what sort of input you are 
expecting for the RFC. Is this about the design itself?
If so, I think it would be more helpful to write an high level document 
on how you plan to emulate the vIOMMU in Xen. So there is one place to 
read/agree/verify rather than trying to collate all the information from 
the 20+ patches.
Briefly skimming through I think the main things that need to be 
addressed in order of priority:
  - How to secure the vIOMMU
  - 1 vs multiple vIOMMU

The questions are very similar to the vITS because the SMMUv3 is based 
on a queue. And given you are selling this feature as a security one, I 
don't think we can go forward with the review without any 
understanding/agreement on what needs to be implemented in order to have 
a safe/secure vIOMMU.
Cheers,

--
Julien Grall