linux-kernel - Re: [PATCH v8 07/10] iommufd: Fault-capable hwpt attach/detach/replace

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Message-ID: <20241015125420.GK1825128@ziepe.ca>
Date: Tue, 15 Oct 2024 09:54:20 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>, 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,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v8 07/10] iommufd: Fault-capable hwpt
 attach/detach/replace

On Tue, Oct 15, 2024 at 11:19:33AM +0800, Zhangfei Gao wrote:
> > +static int iommufd_fault_iopf_enable(struct iommufd_device *idev)
> > +{
> > +       struct device *dev = idev->dev;
> > +       int ret;
> > +
> > +       /*
> > +        * Once we turn on PCI/PRI support for VF, the response failure code
> > +        * should not be forwarded to the hardware due to PRI being a shared
> > +        * resource between PF and VFs. There is no coordination for this
> > +        * shared capability. This waits for a vPRI reset to recover.
> > +        */
> > +       if (dev_is_pci(dev) && to_pci_dev(dev)->is_virtfn)
> > +               return -EINVAL;
> 
> I am using the SMMUv3 stall feature, and need to forward this to hardware,
> And now I am hacking to comment this check.
> Any suggestions?

Are you using PCI SRIOV and stall together?

> > +       mutex_lock(&idev->iopf_lock);
> > +       /* Device iopf has already been on. */
> > +       if (++idev->iopf_enabled > 1) {
> > +               mutex_unlock(&idev->iopf_lock);
> > +               return 0;
> > +       }
> > +
> > +       ret = iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_IOPF);
> > +       if (ret)
> > +               --idev->iopf_enabled;
> > +       mutex_unlock(&idev->iopf_lock);
> 
> Also iommu_dev_enable_feature(idev->dev, IOMMU_DEV_FEAT_SVA); is required
> In thinking how to add it properly.

FEAT_SVA needs to be deleted, not added too.

smmu-v3 needs some more fixing to move that
arm_smmu_master_enable_sva() logic into domain attachment.

Jason