Commit 792fb43c authored by Lu Baolu's avatar Lu Baolu Committed by Joerg Roedel
Browse files

iommu/vt-d: Enable Intel IOMMU scalable mode by default 



The commit 8950dcd8 ("iommu/vt-d: Leave scalable mode default off")
leaves the scalable mode default off and end users could turn it on with
"intel_iommu=sm_on". Using the Intel IOMMU scalable mode for kernel DMA,
user-level device access and Shared Virtual Address have been enabled.
This enables the scalable mode by default if the hardware advertises the
support and adds kernel options of "intel_iommu=sm_on/sm_off" for end
users to configure it through the kernel parameters.

Suggested-by: default avatarAshok Raj <ashok.raj@intel.com>
Suggested-by: default avatarSanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20210720013856.4143880-1-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20210818134852.1847070-5-baolu.lu@linux.intel.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 01dac2d9

Documentation/admin-guide/kernel-parameters.txt

+6 −5
Original line number Diff line number Diff line
@@ -1946,11 +1946,12 @@ 
			By default, super page will be supported if Intel IOMMU

			has the capability. With this option, super page will

			not be supported.

		sm_on [Default Off]

			By default, scalable mode will be disabled even if the

			hardware advertises that it has support for the scalable

			mode translation. With this option set, scalable mode

			will be used on hardware which claims to support it.

		sm_on

			Enable the Intel IOMMU scalable mode if the hardware

			advertises that it has support for the scalable mode

			translation.

		sm_off

			Disallow use of the Intel IOMMU scalable mode.

		tboot_noforce [Default Off]

			Do not force the Intel IOMMU enabled under tboot.

			By default, tboot will force Intel IOMMU on, which

drivers/iommu/intel/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -84,6 +84,7 @@ config INTEL_IOMMU_FLOPPY_WA 


config INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON

	bool "Enable Intel IOMMU scalable mode by default"

	default y

	help

	  Selecting this option will enable by default the scalable mode if

	  hardware presents the capability. The scalable mode is defined in

drivers/iommu/intel/iommu.c

+4 −1
Original line number Diff line number Diff line
@@ -432,8 +432,11 @@ static int __init intel_iommu_setup(char *str) 
			pr_info("Disable supported super page\n");

			intel_iommu_superpage = 0;

		} else if (!strncmp(str, "sm_on", 5)) {

			pr_info("Intel-IOMMU: scalable mode supported\n");

			pr_info("Enable scalable mode if hardware supports\n");

			intel_iommu_sm = 1;

		} else if (!strncmp(str, "sm_off", 6)) {

			pr_info("Scalable mode is disallowed\n");

			intel_iommu_sm = 0;

		} else if (!strncmp(str, "tboot_noforce", 13)) {

			pr_info("Intel-IOMMU: not forcing on after tboot. This could expose security risk for tboot\n");

			intel_iommu_tboot_noforce = 1;