RE: [PATCH v4 1/6] iommu: Add a per domain PASID for DMA API

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Wednesday, June 1, 2022 1:30 AM
> > >
> > > In both cases the pasid is stored in the attach data instead of the
> > > domain.
> > >
> So during IOTLB flush for the domain, do we loop through the attach data?

Yes and it's required.

> 
> > > DMA API pasid is no special from above except it needs to allow
> > > one device attached to the same domain twice (one with RID
> > > and the other with RID+PASID).
> > >
> > > for iommufd those operations are initiated by userspace via
> > > iommufd uAPI.
> >
> > My understanding is that device driver owns its PASID policy. If ENQCMD
> > is supported on the device, the PASIDs should be allocated through
> > ioasid_alloc(). Otherwise, the whole PASID pool is managed by the device
> > driver.
> >
> It seems the changes we want for this patchset are:
> 1. move ioasid_alloc() from the core to device (allocation scope will be
> based on whether ENQCMD is intended or not)

yes, and the driver can specify whether the allocation is system-wide
or per-device.

> 2. store pasid in the attach data
> 3. use the same iommufd api to attach/set pasid on its default domain

s/iommufd/iommu/