linux-kernel - Re: [PATCH v5 3/9] iommu: Add attachment handle to struct iopf

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Message-ID: <20240510133824.GW4718@ziepe.ca>
Date: Fri, 10 May 2024 10:38:24 -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 v5 3/9] iommu: Add attachment handle to struct iopf_group

On Fri, May 10, 2024 at 11:14:20AM +0800, Baolu Lu wrote:
> On 5/8/24 8:04 AM, Jason Gunthorpe wrote:
> > On Tue, Apr 30, 2024 at 10:57:04PM +0800, Lu Baolu wrote:
> > > @@ -206,8 +197,11 @@ void iommu_report_device_fault(struct device *dev, struct iopf_fault *evt)
> > >   	if (group == &abort_group)
> > >   		goto err_abort;
> > > -	group->domain = get_domain_for_iopf(dev, fault);
> > > -	if (!group->domain)
> > > +	if (!(fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID) ||
> > > +	    get_attach_handle_for_iopf(dev, fault->prm.pasid, group))
> > > +		get_attach_handle_for_iopf(dev, IOMMU_NO_PASID, group);
> > That seems a bit weird looking?
> 
> Agreed.
> 
> > get_attach_handle_for_iopf(dev,
> >     (fault->prm.flags &
> >     IOMMU_FAULT_PAGE_REQUEST_PASID_VALID) ? fault->prm.pasid : IOMMU_NO_PASID,
> >     group);
> 
> The logic here is that it tries the PASID domain and if it doesn't
> exist, then tries the RID domain as well. I explained this in the commit
> message:
> 
> "
> ... if the pasid table of a device is wholly managed by user space,
> there is no domain attached to the PASID of the device ...
> "

Okay, it needs a comment in the code, and the RID fallback should be
based aroudn checking for a NESTING domain type which includes the
PASID table. (ie ARM and AMD not Intel)

We shouldn't just elevate a random PASID to the RID if it isn't
approprite..

Jason