[PATCH kernel] powerpc/iommu: Add simple iommu_ops to report capabilities

[Jason Gunthorpe]

On Tue, Jul 05, 2022 at 04:22:35PM +1000, Alexey Kardashevskiy wrote:

> I have not looked into the domains for ages, what is missing here? With this
> on top of 5.19-rc1 VFIO works again on my POWER9 box. Thanks,

Does this solve all the problems or just coherency? It seems like it
should solve everything now as there will be a IOMMU_DOMAIN_BLOCKED
and the ref logic will succeed to assign it?

> +static struct iommu_domain *spapr_tce_iommu_domain_alloc(unsigned int type)
> +{
> +	struct iommu_domain *domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> +
> +	if (!domain)
> +		return NULL;

This should only succeed if type is IOMMU_DOMAIN_BLOCKED

> +static struct iommu_group *spapr_tce_iommu_device_group(struct device *dev)
> +{
> +	struct iommu_group *grp = dev->iommu_group;
> +
> +	if (!grp)
> +		grp = ERR_PTR(-ENODEV);

It looks like this should just always fail since the code code already
checks iommu_group before calling this? (Arguably ppc should be
refactored to use the normal probe_device and device_group ops to
create groups, but that doesn't seem critical for this.

Thanks
Jason