Re: [PATCH v2 8/8] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Aug 30, 2024 at 08:16:27AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Tuesday, August 27, 2024 11:52 PM
> > 
> > For SMMUv3 a IOMMU_DOMAIN_NESTED is composed of a S2
> > iommu_domain acting
> > as the parent and a user provided STE fragment that defines the CD table
> > and related data with addresses translated by the S2 iommu_domain.
> > 
> > The kernel only permits userspace to control certain allowed bits of the
> > STE that are safe for user/guest control.
> > 
> > IOTLB maintenance is a bit subtle here, the S1 implicitly includes the S2
> > translation, but there is no way of knowing which S1 entries refer to a
> > range of S2.
> > 
> > For the IOTLB we follow ARM's guidance and issue a
> > CMDQ_OP_TLBI_NH_ALL to
> > flush all ASIDs from the VMID after flushing the S2 on any change to the
> > S2.
> > 
> > Similarly we have to flush the entire ATC if the S2 is changed.
> 
> it's clearer to mention that ATS is not supported at this point.

I will also move all of this stuff to the ATS enablement patch

> > @@ -2614,7 +2687,8 @@ arm_smmu_find_master_domain(struct
> > arm_smmu_domain *smmu_domain,
> >  	list_for_each_entry(master_domain, &smmu_domain->devices,
> >  			    devices_elm) {
> >  		if (master_domain->master == master &&
> > -		    master_domain->ssid == ssid)
> > +		    master_domain->ssid == ssid &&
> > +		    master_domain->nest_parent == nest_parent)
> >  			return master_domain;
> >  	}
> 
> there are two nest_parent flags in master_domain and smmu_domain.
> Probably duplicating?

Including this

And I will rename master_domain->nest_parent to master_domain->nested_ats_flush
and it will derive from nest_domain->enable_ats.

Which I think will be much clearer..

Thanks,
Jason