RE: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface

[Tian, Kevin]

> From: Jason Gunthorpe <jgg@xxxxxxxx>
> Sent: Wednesday, April 10, 2024 11:42 PM
> 
> On Mon, Mar 25, 2024 at 10:16:54AM +0800, Lu Baolu wrote:
> > +static int __cache_tag_assign_parent_domain(struct dmar_domain
> *domain, u16 did,
> > +					    struct device *dev, ioasid_t pasid)
> > +{
> > +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> > +	int ret;
> > +
> > +	ret = cache_tag_assign(domain, did, dev, pasid,
> CACHE_TAG_TYPE_PARENT_IOTLB);
> > +	if (ret || !info->ats_enabled)
> > +		return ret;
> 
> I'm not sure I understood the point of PARENT_IOTLB? I didn't see any
> different implementation?
> 
> Isn't this backwards though? Each domain should have a list of things
> to invalidate if the domain itself changes.
> 
> So the nesting parent should have a list of CHILD_DEVTLB's that need
> cleaning. That list is changed when the nesting domains are attached
> to something.
> 

probably just a naming confusion. it's called PARENT_IOTLB from the
angle that this domain is used as a parent domain but actually it
tracks the child tags in nested attach.