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

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Message-ID: <f218230c-ae01-4168-b36e-5e502de6b3db@linux.intel.com>
Date: Fri, 18 Oct 2024 09:58:37 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>, Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: 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 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;
	}

Thanks,
baolu