[PATCH 1/1] iommu/vt-d: Add Kconfig option to enable/disable scalable mode

[Lu Baolu]

This adds a Kconfig option INTEL_IOMMU_SCALABLE_MODE_ON to make
it easier for distributions to enable or disable the Intel IOMMU
scalable mode during kernel build.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/Kconfig       | 10 ++++++++++
 drivers/iommu/intel-iommu.c |  5 +++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index e3842eabcfdd..32f30e27791c 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -242,6 +242,16 @@ config INTEL_IOMMU_FLOPPY_WA
 	  workaround will setup a 1:1 mapping for the first
 	  16MiB to make floppy (an ISA device) work.
 
+config INTEL_IOMMU_SCALABLE_MODE_ON
+	def_bool n
+	prompt "Enable Intel IOMMU scalable mode by default"
+	depends on INTEL_IOMMU
+	help
+	  Selecting this option will enable the scalable mode if
+	  hardware presents the capability. If this option is not
+	  selected, scalable mode support could also be enabled
+	  by passing intel_iommu=sm_on to the kernel.
+
 config IRQ_REMAP
 	bool "Support for Interrupt Remapping"
 	depends on X86_64 && X86_IO_APIC && PCI_MSI && ACPI
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0f2f7124c1ca..545eb3b5c083 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -357,7 +357,12 @@ int dmar_disabled = 0;
 int dmar_disabled = 1;
 #endif /*CONFIG_INTEL_IOMMU_DEFAULT_ON*/
 
+#ifdef CONFIG_INTEL_IOMMU_SCALABLE_MODE_ON
+int intel_iommu_sm = 1;
+#else
 int intel_iommu_sm;
+#endif /* CONFIG_INTEL_IOMMU_SCALABLE_MODE_ON */
+
 int intel_iommu_enabled = 0;
 EXPORT_SYMBOL_GPL(intel_iommu_enabled);
 
-- 
2.17.1