linux-kernel - Re: [PATCH v2 3/8] iommu/vt-d: Implement device

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Message-ID: <20220315152318.262dd0bf@jacob-builder>
Date:   Tue, 15 Mar 2022 15:23:18 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        "Jason Gunthorpe" <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 3/8] iommu/vt-d: Implement device_pasid domain attach
 ops

Hi Kevin,

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

> > From: Jacob Pan <jacob.jun.pan@...ux.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@...ux.intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.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