path: root/Documentation/kernel-parameters.txt
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2015-06-12 11:28:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-12 11:28:57 -0700
commitc39f3bc659b6f32e0e88113ec359a504be259e4f (patch)
tree2eb1ddf4f039dda7fed72f57162df3561e78214a /Documentation/kernel-parameters.txt
parentdf5f4158415b6fc4a2d683c6fdc806be6da176bc (diff)
parentc83b2f20fdde578bded3dfc4405c5db7a039c694 (diff)
Merge git://git.infradead.org/intel-iommu
Pull VT-d hardware workarounds from David Woodhouse: "This contains a workaround for hardware issues which I *thought* were never going to be seen on production hardware. I'm glad I checked that before the 4.1 release... Firstly, PASID support is so broken on existing chips that we're just going to declare the old capability bit 28 as 'reserved' and change the VT-d spec to move PASID support to another bit. So any existing hardware doesn't support SVM; it only sets that (now) meaningless bit 28. That patch *wasn't* imperative for 4.1 because we don't have PASID support yet. But *even* the extended context tables are broken — if you just enable the wider tables and use none of the new bits in them, which is precisely what 4.1 does, you find that translations don't work. It's this problem which I thought was caught in time to be fixed before production, but wasn't. To avoid triggering this issue, we now *only* enable the extended context tables on hardware which also advertises "we have PASID support and we actually tested it this time" with the new PASID feature bit. In addition, I've added an 'intel_iommu=ecs_off' command line parameter to allow us to disable it manually if we need to" * git://git.infradead.org/intel-iommu: iommu/vt-d: Only enable extended context tables if PASID is supported iommu/vt-d: Change PASID support to bit 40 of Extended Capability Register
Diffstat (limited to 'Documentation/kernel-parameters.txt')
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 61ab1628a057..6726139bd289 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1481,6 +1481,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
By default, super page will be supported if Intel IOMMU
has the capability. With this option, super page will
not be supported.
+ ecs_off [Default Off]
+ By default, extended context tables will be supported if
+ the hardware advertises that it has support both for the
+ extended tables themselves, and also PASID support. With
+ this option set, extended tables will not be used even
+ on hardware which claims to support them.
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
0 disables intel_idle and fall back on acpi_idle.

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