Re: [PATCH 7/7] iommu: Add iommu_domain::domain_ops

[Jean-Philippe Brucker]

On Mon, Jan 24, 2022 at 09:58:18AM +0000, Tian, Kevin wrote:
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Monday, January 24, 2022 3:11 PM
> > +/**
> > + * struct domain_ops - per-domain ops
> > + * @attach_dev: attach an iommu domain to a device
> > + * @detach_dev: detach an iommu domain from a device
> 
> What is the criteria about whether an op should be iommu_ops or domain_ops
> when it requires both domain and device pointers like above two (and future
> PASID-based attach)?
> 
> Other examples include:
> 	@apply_resv_region
> 	@is_attach_deferred

Could attach_dev() be an IOMMU op?  So a driver could set the domain ops
in attach_dev() rather than domain_alloc(). That would allow to install
map()/unmap() ops that are tailored for the device's IOMMU, which we don't
know at domain_alloc() time. I'm thinking about a guest that has both
physical and virtual endpoints, which would ideally use different kinds of
domain ops to support both efficiently (caching mode vs page tables)

Thanks,
Jean