Re: [RFC PATCH v2 00/58] KVM: Arm SMMUv3 driver for pKVM

[Mostafa Saleh <smostafa@google.com>]

On Thu, Jan 16, 2025 at 03:19:52PM -0400, Jason Gunthorpe wrote:
> On Wed, Jan 08, 2025 at 12:09:53PM +0000, Mostafa Saleh wrote:
> 
> > I am open to gradually upstream this as you mentioned where as a first
> > step pKVM would establish DMA isolation without translation for host,
> > that should be enough to have functional pKVM and run protected workloads.
> 
> Personally I hate these giant patch series, you should strip it down
> to small meaningful steps and try to stay below 20 per series.
> 
> I think getting pkvm to own the SMMU HW is a great first step that
> everything else can build on

I plan to do that for v3, I think that also removes the out-of-tree
dependencies, so the code applies directly on upstream.
Thanks for the feedback!

> 
> > But although that might be usable on some systems, I don’t think that’s
> > practical in the long term as it limits the amount of HW that can run pKVM.
> 
> I suspect you will end up doing everything. Old HW needs paravirt, new
> HW will want nesting and its performance. Users other than mobile will
> come. If we were to use pKVM on server workloads we need nesting for
> performance.

Yes, I guess that would be the case, as I mentioned in another reply
it would be interesting to get the order of magnitude both, which I am
looking into, I hope it'd help with which direction we should
prioritize upstream.

Thanks,
Mostafa

> 
> Jason