From 8950dcd83ae7d62bdc2a60507949acebd85399f2 Mon Sep 17 00:00:00 2001 From: Lu Baolu Date: Thu, 24 Jan 2019 10:31:32 +0800 Subject: iommu/vt-d: Leave scalable mode default off Commit 765b6a98c1de3 ("iommu/vt-d: Enumerate the scalable mode capability") enables VT-d scalable mode if hardware advertises the capability. As we will bring up different features and use cases to upstream in different patch series, it will leave some intermediate kernel versions which support partial features. Hence, end user might run into problems when they use such kernels on bare metals or virtualization environments. This leaves scalable mode default off and end users could turn it on with "intel-iommu=sm_on" only when they have clear ideas about which scalable features are supported in the kernel. Cc: Liu Yi L Cc: Jacob Pan Suggested-by: Ashok Raj Suggested-by: Kevin Tian Signed-off-by: Lu Baolu Signed-off-by: Joerg Roedel --- Documentation/admin-guide/kernel-parameters.txt | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b799bcf67d7b..858b6c0b9a15 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1696,12 +1696,11 @@ By default, super page will be supported if Intel IOMMU has the capability. With this option, super page will not be supported. - sm_off [Default Off] - By default, scalable mode will be supported if the + 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 not be used even on hardware which claims to support - it. + will be used on hardware which claims to support it. tboot_noforce [Default Off] Do not force the Intel IOMMU enabled under tboot. By default, tboot will force Intel IOMMU on, which -- cgit v1.2.3-59-g8ed1b