linux-kernel - Re: [PATCH v2 5/8] iommu: Add PASID support for DMA mapping API users

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Date:   Tue, 15 Mar 2022 20:05:49 -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>,
        Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH v2 5/8] iommu: Add PASID support for DMA mapping API users

On Tue, Mar 15, 2022 at 09:38:10AM -0700, Jacob Pan wrote:
> > > +int iommu_enable_pasid_dma(struct device *dev, ioasid_t *pasid)
> > > +{
> > > +	struct iommu_domain *dom;
> > > +	ioasid_t id, max;
> > > +	int ret;
> > > +
> > > +	dom = iommu_get_domain_for_dev(dev);
> > > +	if (!dom || !dom->ops || !dom->ops->attach_dev_pasid)
> > > +		return -ENODEV;  
> > 
> > Given the purpose of this API I think it should assert that the device
> > has the DMA API in-use using the machinery from the other series.
> > 
> > ie this should not be used to clone non-DMA API iommu_domains..
> > 
> Let me try to confirm the specific here. I should check domain type and
> rejects all others except IOMMU_DOMAIN_DMA type, right? Should also allow
> IOMMU_DOMAIN_IDENTITY.
> 
> That makes sense.

That is one way, the other is to check the new group data that Lu's
patch added.

Jason