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

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Message-ID: <20241018143306.GN948948@ziepe.ca>
Date: Fri, 18 Oct 2024 11:33:06 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Zhangfei Gao <zhangfei.gao@...aro.org>,
	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 Fri, Oct 18, 2024 at 09:58:37AM +0800, Baolu Lu wrote:
> On 2024/10/17 21:08, Jason Gunthorpe wrote:
> > On Thu, Oct 17, 2024 at 08:35:24PM +0800, Zhangfei Gao wrote:
> > 
> > > Yes, you are right
> > >   I am using SRIOV vf and stall feature, so is_virtfn == true
> > > 
> > > Our ACC devices are fake pci endpoint devices which supports stall,
> > > And they also supports sriov
> > > 
> > > So I have to ignore the limitation.
> > I see, so that is more complicated.
> > 
> > Lu, what do you think about also checking if the PCI function has PRI
> > ? If not PRI assume the fault is special and doesn't follow PRI rules?
> > 
> > Or maybe we can have the iommu driver tag the event as a PRI/not-PRI
> > fault?
> 
> This limitation applies to PRI on PCI/SRIOV VFs because the PRI might be
> a shared resource and current iommu subsystem is not ready to support
> enabling/disabling PRI on a VF without any impact on others.
> 
> In my understanding, it's fine to remove this limitation from the use
> case of non-PRI on SRIOV VFs. Perhaps something like below?
> 
> 	if (dev_is_pci(dev)) {
> 		struct pci_dev *pdev = to_pci_dev(dev);
> 		if (pdev->is_virtfn && pci_pri_supported(pdev))
> 			return -EINVAL;
> 	}

Makes sense to me

Thanks,
Jason