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

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Message-ID: <50ee0c0b052b40f6b67d1ad3b1b0eeb9@huawei.com>
Date: Thu, 17 Oct 2024 12:58:13 +0000
From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To: Zhangfei Gao <zhangfei.gao@...aro.org>, Jason Gunthorpe <jgg@...pe.ca>
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" <iommu@...ts.linux.dev>,
	"virtualization@...ts.linux-foundation.org"
	<virtualization@...ts.linux-foundation.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v8 07/10] iommufd: Fault-capable hwpt
 attach/detach/replace



> -----Original Message-----
> From: Zhangfei Gao <zhangfei.gao@...aro.org>
> Sent: Thursday, October 17, 2024 1:35 PM
> To: Jason Gunthorpe <jgg@...pe.ca>
> 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 Thu, 17 Oct 2024 at 20:05, Jason Gunthorpe <jgg@...pe.ca> wrote:
> >
> > On Thu, Oct 17, 2024 at 09:44:18AM +0800, Zhangfei Gao wrote:
> > > On Wed, 16 Oct 2024 at 23:25, Jason Gunthorpe <jgg@...pe.ca> wrote:
> > > >
> > > > On Wed, Oct 16, 2024 at 09:58:36AM +0800, Zhangfei Gao wrote:
> > > > > On Tue, 15 Oct 2024 at 20:54, Jason Gunthorpe <jgg@...pe.ca>
> wrote:
> > > > > >
> > > > > > 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?
> > > > >
> > > > > Only use smmuv3 stall feature.
> Sorry, this is not correct
> 
> > > >
> > > > Then isn't to_pci_dev(dev)->is_virtfn == false?
> > > >
> > > > That should only be true with SRIOV
> > >
> > > Do you mean
> > > if (dev_is_pci(dev) && to_pci_dev(dev)->is_virtfn == false)
> > >     return -EINVAL;
> > >
> > > This is fine
> >
> > No, I mean on your test system you are not using SRIOV so all your PCI
> > devices will have is_virtfn == false and the above if shouldn't be a
> > problem. is_virtfn indicates the PCI device is a SRIOV VF.
> >
> > Your explanation for your problem doesn't really make sense, or there
> > is something wrong someplace else to get a bogus is_virtfn..
> >
> > If you are doing SRIOV with stall, then that is understandable.
> 
> 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

May be this will help to get the background:
https://lore.kernel.org/all/1626144876-11352-1-git-send-email-zhangfei.gao@linaro.org/

Shameer