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

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The commit 8950dcd83a ("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: Ashok Raj <ashok.raj@intel.com>
Suggested-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Lu 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: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Lu Baolu 2021-08-18 21:48:47 +08:00 committed by Joerg Roedel
parent 01dac2d9d2
commit 792fb43ce2
3 changed files with 11 additions and 6 deletions
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11
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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

1
drivers/iommu/intel/Kconfig
View File

@ -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

5
drivers/iommu/intel/iommu.c
View File

@ -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;