Re: [PATCH v1 08/12] iommufd/viommu: Replace ops->viommu_alloc with ops->viommu_init

[Nicolin Chen <nicolinc@nvidia.com>]

On Thu, Jun 12, 2025 at 08:22:49AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Tuesday, June 10, 2025 2:20 PM
> > 
> > On Tue, Jun 10, 2025 at 01:55:05PM +0800, Baolu Lu wrote:
> > > On 6/10/25 01:13, Nicolin Chen wrote:
> > > > To ease the for-driver iommufd APIs, get_viommu_size and viommu_init
> > ops
> > > > are introduced. Now, those existing vIOMMU supported drivers
> > implemented
> > > > these two ops too.
> > > >
> > > > Relace the ops->viommu_alloc call with the two new ones.
> > > >
> > > > Note that this will fail a !viommu->ops case from now on, since a
> > vIOMMU
> > > > is expected to support alloc_domain_nested at least.
> > >
> > > Does this mean that the viommu implementation in the iommu driver is
> > > required to implement alloc_domain_nested? I suppose viommu should
> > soon
> > > be extended to support TEE/IO.
> > 
> > It's a good point that CCA might not need a nested domain. So,
> > it's inaccurate to say that, although I suspect that CCA would
> > need some other viommu op then the check here would be sane.
> > 
> > With that being said, it's probably not worth adding that until
> > we are 100% sure that no case will work with a !viommu->ops, so
> > let's drop this new rejection, since we haven't had it so far.
> > 
> 
> WARN_ON_ONCE() is built on the current context, not the future
> usage. So I'd prefer to keeping it until there is a real need to revert.
> 
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Okay. And I can make the commit message clearer.

Thanks
Nicolin