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, 15 Feb 2023 20:44:02 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Felix Kuehling <felix.kuehling@....com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Baolu Lu <baolu.lu@...ux.intel.com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Liu, Aaron" <Aaron.Liu@....com>, Joerg Roedel <jroedel@...e.de>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        "Hegde, Vasant" <Vasant.Hegde@....com>,
        amd-gfx@...ts.freedesktop.org, LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Matt Fagnani <matt.fagnani@...l.net>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [regression, bisected, pci/iommu] Bug 216865 - Black screen when
 amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled

On Wed, Feb 15, 2023 at 07:35:45PM -0500, Felix Kuehling wrote:
> 
> If I understand this correctly, the HW or the BIOS is doing something wrong
> about reporting ACS. I don't know what the GPU driver can do other than add
> some quirk to stop using AMD IOMMUv2 on this HW/BIOS.

How about this:

diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
index 864e4ffb6aa94e..cc027ce9a6e86f 100644
--- a/drivers/iommu/amd/iommu_v2.c
+++ b/drivers/iommu/amd/iommu_v2.c
@@ -732,6 +732,7 @@ EXPORT_SYMBOL(amd_iommu_unbind_pasid);
 
 int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
 {
+	struct iommu_dev_data *dev_data = dev_iommu_priv_get(&pdev->dev);
 	struct device_state *dev_state;
 	struct iommu_group *group;
 	unsigned long flags;
@@ -740,6 +741,9 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
 
 	might_sleep();
 
+	if (!dev_data->ats.enabled)
+		return -EINVAL;
+
 	/*
 	 * When memory encryption is active the device is likely not in a
 	 * direct-mapped domain. Forbid using IOMMUv2 functionality for now.