iommu/amd: Enhance def_domain_type to handle untrusted device

Previously, IOMMU core layer was forcing IOMMU_DOMAIN_DMA domain for
untrusted device. This always took precedence over driver's
def_domain_type(). Commit 59ddce4 ("iommu: Reorganize
iommu_get_default_domain_type() to respect def_domain_type()") changed
the behaviour. Current code calls def_domain_type() but if it doesn't
return IOMMU_DOMAIN_DMA for untrusted device it throws error. This
results in IOMMU group (and potentially IOMMU itself) in undetermined
state.

This patch adds untrusted check in AMD IOMMU driver code. So that it
allows eGPUs behind Thunderbolt work again.

Fine tuning amd_iommu_def_domain_type() will be done later.

Reported-by: Eric Wagner <[email protected]>
Link: https://lore.kernel.org/linux-iommu/CAHudX3zLH6CsRmLE-yb+gRjhh-v4bU5_1jW_xCcxOo_oUUZKYg@mail.gmail.com
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3182
Fixes: 59ddce4 ("iommu: Reorganize iommu_get_default_domain_type() to respect def_domain_type()")
Cc: Robin Murphy <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: [email protected] # v6.7+
Signed-off-by: Vasant Hegde <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

drivers/iommu/amd/iommu.c

@@ -2754,6 +2754,10 @@ static int amd_iommu_def_domain_type(struct device *dev)
 	if (!dev_data)
 		return 0;
 
+	/* Always use DMA domain for untrusted device */
+	if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
+		return IOMMU_DOMAIN_DMA;
+
 	/*
 	 * Do not identity map IOMMUv2 capable devices when:
 	 *  - memory encryption is active, because some of those devices