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Date:   Tue, 23 Aug 2022 17:28:24 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <jroedel@suse.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Eric Auger <eric.auger@redhat.com>,
        regressions@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [REGRESSION 5.19.x] AMD HD-audio devices missing on 5.19
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On Tue, Aug 23, 2022 at 01:46:36PM +0200, Takashi Iwai wrote:
> It was tested now and confirmed that the call path is via AMDGPU, as
> expected:
>   amdgpu_pci_probe ->
>   amdgpu_driver_load_kms ->
>   amdgpu_device_init ->
>   amdgpu_amdkfd_device_init ->
>   kgd2kfd_device_init ->
>   kgd2kfd_resume_iommu ->
>   kfd_iommu_resume ->
>   amd_iommu_init_device ->
>   iommu_attach_group ->
>   __iommu_attach_group

Oh, when you said sound intel I thought this was an Intel CPU..

Yes, there is this hacky private path from the amdgpu to
the amd iommu driver that makes a mess of it here. We discussed it in
this thread:

https://lore.kernel.org/linux-iommu/YgtuJQhY8SNlv9%2F6@8bytes.org/

But nobody put it together that it would be a problem with this.

Something like this, perhaps, but I didn't check if overriding the
type would cause other problems.

diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
index 696d5555be5794..6a1f02c62dffcc 100644
--- a/drivers/iommu/amd/iommu_v2.c
+++ b/drivers/iommu/amd/iommu_v2.c
@@ -777,6 +777,8 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
 	if (dev_state->domain == NULL)
 		goto out_free_states;
 
+	/* See iommu_is_default_domain() */
+	dev_state->domain->type = IOMMU_DOMAIN_IDENTITY;
 	amd_iommu_domain_direct_map(dev_state->domain);
 
 	ret = amd_iommu_domain_enable_v2(dev_state->domain, pasids);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 780fb70715770d..fe8bd17f52314b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3076,6 +3076,24 @@ static ssize_t iommu_group_store_type(struct iommu_group *group,
 	return ret;
 }
 
+static bool iommu_is_default_domain(struct iommu_group *group)
+{
+	if (group->domain == group->default_domain)
+		return true;
+
+	/*
+	 * If the default domain was set to identity and it is still an identity
+	 * domain then we consider this a pass. This happens because of
+	 * amd_iommu_init_device() replacing the default idenity domain with an
+	 * identity domain that has a different configuration for AMDGPU.
+	 */
+	if (group->default_domain &&
+	    group->default_domain->type == IOMMU_DOMAIN_IDENTITY &&
+	    group->domain && group->domain->type == IOMMU_DOMAIN_IDENTITY)
+		return true;
+	return false;
+}
+
 /**
  * iommu_device_use_default_domain() - Device driver wants to handle device
  *                                     DMA through the kernel DMA API.
@@ -3094,8 +3112,7 @@ int iommu_device_use_default_domain(struct device *dev)
 
 	mutex_lock(&group->mutex);
 	if (group->owner_cnt) {
-		if (group->domain != group->default_domain ||
-		    group->owner) {
+		if (group->owner || iommu_is_default_domain(group)) {
 			ret = -EBUSY;
 			goto unlock_out;
 		}