x86, AMD IOMMU: add early detection code

This patch adds code to detect an AMD IOMMU early during boot before the early
detection code of other IOMMUs run.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Cc: Sebastian.Biemueller@amd.com
Cc: robert.richter@amd.com
Cc: joro@8bytes.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index c792ddc4fec6..d7a75bf0f7e6 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -769,3 +769,23 @@ free:
         goto out;
 }
 
+static int __init early_amd_iommu_detect(struct acpi_table_header *table)
+{
+        return 0;
+}
+
+void __init amd_iommu_detect(void)
+{
+        if (swiotlb || no_iommu || iommu_detected)
+                return;
+
+        if (amd_iommu_disable)
+                return;
+
+        if (acpi_table_parse("IVRS", early_amd_iommu_detect) == 0) {
+                iommu_detected = 1;
+                gart_iommu_aperture_disabled = 1;
+                gart_iommu_aperture = 0;
+        }
+}
+