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

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Message-ID: <CABQgh9GU4xp=7Svs_Ni=bvNKECKKUjHgq4d-FjT5Y_4wu44kDA@mail.gmail.com>
Date: Fri, 18 Oct 2024 10:45:11 +0800
From: Zhangfei Gao <zhangfei.gao@...aro.org>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>, 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

Hi, Baolu

On Fri, 18 Oct 2024 at 09:58, Baolu Lu <baolu.lu@...ux.intel.com> 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?
>
#include <linux/pci-ats.h>
>         if (dev_is_pci(dev)) {
>                 struct pci_dev *pdev = to_pci_dev(dev);
>                 if (pdev->is_virtfn && pci_pri_supported(pdev))
>                         return -EINVAL;
>         }

Yes, this works on our platform.

Thanks Baolu.