linux-kernel - Re: [PATCH v4 3/6] iommu/vt-d: Implement domain ops for attach_dev

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Date:   Tue, 24 May 2022 15:02:41 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>, dmaengine@...r.kernel.org,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>, vkoul@...nel.org,
        robin.murphy@....com, will@...nel.org, Yi Liu <yi.l.liu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Eric Auger <eric.auger@...hat.com>
Subject: Re: [PATCH v4 3/6] iommu/vt-d: Implement domain ops for
 attach_dev_pasid

On Tue, May 24, 2022 at 09:12:35AM -0700, Jacob Pan wrote:
> Hi Jason,
> 
> On Tue, 24 May 2022 10:51:35 -0300, Jason Gunthorpe <jgg@...dia.com> wrote:
> 
> > On Wed, May 18, 2022 at 11:21:17AM -0700, Jacob Pan wrote:
> > > On VT-d platforms with scalable mode enabled, devices issue DMA requests
> > > with PASID need to attach PASIDs to given IOMMU domains. The attach
> > > operation involves the following:
> > > - Programming the PASID into the device's PASID table
> > > - Tracking device domain and the PASID relationship
> > > - Managing IOTLB and device TLB invalidations
> > > 
> > > This patch add attach_dev_pasid functions to the default domain ops
> > > which is used by DMA and identity domain types. It could be extended to
> > > support other domain types whenever necessary.
> > > 
> > > 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 | 72 +++++++++++++++++++++++++++++++++++--
> > >  1 file changed, 70 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > > index 1c2c92b657c7..75615c105fdf 100644
> > > +++ b/drivers/iommu/intel/iommu.c
> > > @@ -1556,12 +1556,18 @@ static void __iommu_flush_dev_iotlb(struct
> > > device_domain_info *info, u64 addr, unsigned int mask)
> > >  {
> > >  	u16 sid, qdep;
> > > +	ioasid_t pasid;
> > >  
> > >  	if (!info || !info->ats_enabled)
> > >  		return;
> > >  
> > >  	sid = info->bus << 8 | info->devfn;
> > >  	qdep = info->ats_qdep;
> > > +	pasid = iommu_get_pasid_from_domain(info->dev,
> > > &info->domain->domain);  
> > 
> > No, a simgple domain can be attached to multiple pasids, all need to
> > be flushed.
> > 
> Here is device TLB flush, why would I want to flush PASIDs other than my
> own device attached?

Again, a domain can be attached to multiple PASID's *on the same
device*

The idea that there is only one PASID per domain per device is not
right.

Jason