linux-kernel - Re: [PATCH v4 2/9] iommu: Replace sva_iommu with iommu_attach

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Message-ID: <20240408141946.GB223006@ziepe.ca>
Date: Mon, 8 Apr 2024 11:19:46 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Nicolin Chen <nicolinc@...dia.com>, Yi Liu <yi.l.liu@...el.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Joel Granados <j.granados@...sung.com>, iommu@...ts.linux.dev,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/9] iommu: Replace sva_iommu with iommu_attach_handle

On Sat, Apr 06, 2024 at 02:09:34PM +0800, Baolu Lu wrote:
> On 4/3/24 7:59 PM, Jason Gunthorpe wrote:
> > On Wed, Apr 03, 2024 at 09:15:12AM +0800, Lu Baolu wrote:
> > > +	/* A bond already exists, just take a reference`. */
> > > +	handle = iommu_attach_handle_get(group, iommu_mm->pasid);
> > > +	if (handle) {
> > > +		mutex_unlock(&iommu_sva_lock);
> > > +		return handle;
> > >   	}
> > At least in this context this is not enough we need to ensure that the
> > domain on the PASID is actually an SVA domain and it was installed by
> > this mechanism, not an iommufd domain for instance.
> > 
> > ie you probably need a type field in the iommu_attach_handle to tell
> > what the priv is.
> > 
> > Otherwise this seems like a great idea!
> 
> Yes, you are right. For the SVA case, I will add the following changes.
> The IOMMUFD path will also need such enhancement. I will update it in
> the next version.

The only use for this is the PRI callbacks right? Maybe instead of
adding a handle type let's just check domain->iopf_handler  ?

Ie SVA will pass &ommu_sva_iopf_handler as its "type"

Jason