x86/amd-iommu: Add amd_iommu=off command line option

This patch adds a command line option to tell the AMD IOMMU
driver to not initialize any IOMMU it finds.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

2 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 839b21b0699a..0c6c56076d19 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -324,6 +324,8 @@ and is between 256 and 4096 characters. It is defined in the file
                                     they are unmapped. Otherwise they are
                                     flushed before they will be reused, which
                                     is a lot of faster
+                        off       - do not initialize any AMD IOMMU found in
+                                    the system
 
         amijoy.map=     [HW,JOY] Amiga joystick support
                         Map of devices attached to JOY0DAT and JOY1DAT
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 6360abf993d4..3bacb4d0844c 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -120,6 +120,7 @@ struct ivmd_header {
 bool amd_iommu_dump;
 
 static int __initdata amd_iommu_detected;
+static bool __initdata amd_iommu_disabled;
 
 u16 amd_iommu_last_bdf;                 /* largest PCI device id we have
                                            to handle */
@@ -1372,6 +1373,9 @@ void __init amd_iommu_detect(void)
         if (no_iommu || (iommu_detected && !gart_iommu_aperture))
                 return;
 
+        if (amd_iommu_disabled)
+                return;
+
         if (acpi_table_parse("IVRS", early_amd_iommu_detect) == 0) {
                 iommu_detected = 1;
                 amd_iommu_detected = 1;
@@ -1401,6 +1405,8 @@ static int __init parse_amd_iommu_options(char *str)
         for (; *str; ++str) {
                 if (strncmp(str, "fullflush", 9) == 0)
                         amd_iommu_unmap_flush = true;
+                if (strncmp(str, "off", 3) == 0)
+                        amd_iommu_disabled = true;
         }
 
         return 1;