linux-kernel - Re: [regression, bisected, pci/iommu] Bug 216865 - Black screen when amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled

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Date:   Wed, 11 Jan 2023 09:08:39 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Vasant Hegde <vasant.hegde@....com>,
        Matt Fagnani <matt.fagnani@...l.net>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Joerg Roedel <jroedel@...e.de>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        LKML <linux-kernel@...r.kernel.org>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        amd-gfx@...ts.freedesktop.org
Subject: Re: [regression, bisected, pci/iommu] Bug 216865 - Black screen when
 amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled

On Wed, Jan 11, 2023 at 11:16:32AM +0800, Baolu Lu wrote:
> On 2023/1/10 21:25, Jason Gunthorpe wrote:
> > > +       } else {
> > > +               if (!pdev->bus->self ||
> > > +                   !pci_acs_path_enabled(pdev->bus->self, NULL,
> > > +                                         PCI_ACS_RR | PCI_ACS_UF))
> > > +                       return -EINVAL;
> > > +       }
> > Why would these be exclusive? Both the path and endpoint needs to be
> > checked
> 
> If the device is not an MFD, do we still need to check the ACS on it?
> Perhaps I didn't get your point correctly.

It always needs to check the path

Jason