Re: [PATCH v2 3/8] iommu/vt-d: Implement device_pasid domain attach ops

Jacob Pan
2022-03-15T22:20:11Z

Hi Kevin,

On Tue, 15 Mar 2022 10:33:08 +0000, "Tian, Kevin" <kevin.tian@intel.com>
wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Tuesday, March 15, 2022 1:07 PM
> >
> > On VT-d platforms with scalable mode enabled, devices issue DMA requests
> > with PASID need to attach to the correct IOMMU domains.
> > The attach operation involves the following:
> > - programming the PASID into device's PASID table
> > - tracking device domain and the PASID relationship
> > - managing IOTLB and device TLB invalidations
> >
> > This patch extends DMAR domain and device domain info with xarrays to
> > track per domain and per device PASIDs. It provides the flexibility to
> > be used beyond DMA API PASID support.
> >
> > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> > drivers/iommu/intel/iommu.c | 194
> > +++++++++++++++++++++++++++++++++++-
> > include/linux/intel-iommu.h | 12 ++-
> > 2 files changed, 202 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 881f8361eca2..9267194eaed3 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -1622,20 +1622,48 @@ static void __iommu_flush_dev_iotlb(struct
> > device_domain_info *info,
> > qdep, addr, mask);
> > }
> >
> > +static void __iommu_flush_dev_piotlb(struct device_domain_info *info,
>
> piotlb is confusing, better be:
>
> __iommu_flush_dev_iotlb_pasid()
>
yeah, that is more clear.

> > + u64 address,
> > + ioasid_t pasid, unsigned int mask)
> > +{
> > + u16 sid, qdep;
> > +
> > + if (!info || !info->ats_enabled)
> > + return;
> > +
> > + sid = info->bus << 8 | info->devfn;
> > + qdep = info->ats_qdep;
> > + qi_flush_dev_iotlb_pasid(info->iommu, sid, info->pfsid,
> > + pasid, qdep, address, mask);
> > +}
> > +
> > static void iommu_flush_dev_iotlb(struct dmar_domain *domain,
> > u64 addr, unsigned mask)
> > {
> > unsigned long flags;
> > struct device_domain_info *info;
> > struct subdev_domain_info *sinfo;
> > + unsigned long pasid;
> > + struct pasid_info *pinfo;
> >
> > if (!domain->has_iotlb_device)
> > return;
> >
> > spin_lock_irqsave(&device_domain_lock, flags);
> > - list_for_each_entry(info, &domain->devices, link)
> > - __iommu_flush_dev_iotlb(info, addr, mask);
> > -
> > + list_for_each_entry(info, &domain->devices, link) {
> > + /*
> > + * We cannot use PASID based devTLB invalidation on
> > RID2PASID
> > + * Device does not understand RID2PASID/0. This is
> > different
>
> Lack of a conjunction word between 'RID2PASID' and 'Device'.
>
> and what is RID2PASID/0? It would be clearer to point out that RID2PASID
> is visible only within the iommu to mark out requests without PASID,
> thus this PASID value should never be sent to the device side.
>
Good point, will do.

> > + * than IOTLB invalidation where RID2PASID is also
> > used for
> > + * tagging.
>
> Then it would be obvious because IOTLB is iommu internal agent thus takes
> use of RID2PASID for tagging.
>
ditto

> > + */
> > + xa_for_each(&info->pasids, pasid, pinfo) {
> > + if (!pasid)
>
> this should be compared to PASID_RID2PASID (though it's zero today).
>
ditto

> > + __iommu_flush_dev_iotlb(info, addr,
> > mask);
> > + else
> > + __iommu_flush_dev_piotlb(info, addr,
> > pasid, mask);
> > + }
> > + }
> > list_for_each_entry(sinfo, &domain->subdevices, link_domain) {
> > info = get_domain_info(sinfo->pdev);
> > __iommu_flush_dev_iotlb(info, addr, mask);
>
> Thanks
> Kevin

Thanks,

Jacob