x86, AMD IOMMU: don't try to init IOMMU if early detect code did not detect one

This patch adds a check if the early detect code has found AMD IOMMU hardware
descriptions and does not try to initialize hardware if the check failed.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index c54c82305af..c970fac6fdc 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -101,6 +101,8 @@ struct ivmd_header {
         u64 range_length;
 } __attribute__((packed));
 
+static int __initdata amd_iommu_detected;
+
 u16 amd_iommu_last_bdf;
 struct list_head amd_iommu_unity_map;
 unsigned amd_iommu_aperture_order = 26;
@@ -689,6 +691,9 @@ int __init amd_iommu_init(void)
                 return 0;
         }
 
+        if (!amd_iommu_detected)
+                return -ENODEV;
+
         /*
          * First parse ACPI tables to find the largest Bus/Dev/Func
          * we need to handle. Upon this information the shared data
@@ -831,6 +836,7 @@ void __init amd_iommu_detect(void)
 
         if (acpi_table_parse("IVRS", early_amd_iommu_detect) == 0) {
                 iommu_detected = 1;
+                amd_iommu_detected = 1;
 #ifdef CONFIG_GART_IOMMU
                 gart_iommu_aperture_disabled = 1;
                 gart_iommu_aperture = 0;