IOMMU Extended Feature Register (EFR) is used to communicate
the supported features for each IOMMU to the IOMMU driver.
This is normally read from the PCI MMIO register offset 0x30,
and used by the iommu_feature() helper function.

However, there are certain scenarios where the information is needed
prior to PCI initialization, and the iommu_feature() function is used
prematurely w/o warning. This has caused incorrect initialization of IOMMU.
This is the case for the commit 6d39bdee ("iommu/amd: Enforce 4k
mapping for certain IOMMU data structures")

Since, the EFR is also available in the IVHD header, and is available to
the driver prior to PCI initialization. Therefore, default to using
the IVHD EFR instead.

Fixes: 6d39bdee ("iommu/amd: Enforce 4k mapping for certain IOMMU data structures")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Robert Richter <rrichter@amd.com>
Link: https://lore.kernel.org/r/20210120135002.2682-1-suravee.suthikulpanit@amd.comSigned-off-by: Joerg Roedel <jroedel@suse.de>