thunderbolt: Introduce USB only (SL4) security level

[sfrench/cifs-2.6.git] / Documentation / admin-guide / thunderbolt.rst

diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst
index 9948ec36a204f9927821f529f57353b046efee38..35fccba6a9a6b4d247e590f8a9e535203015b2b4 100644 (file)
--- a/Documentation/admin-guide/thunderbolt.rst
+++ b/Documentation/admin-guide/thunderbolt.rst
@@ -21,11 +21,11 @@ vulnerable to DMA attacks.
 Security levels and how to use them
 -----------------------------------
 Starting with Intel Falcon Ridge Thunderbolt controller there are 4
-security levels available. The reason for these is the fact that the
-connected devices can be DMA masters and thus read contents of the host
-memory without CPU and OS knowing about it. There are ways to prevent
-this by setting up an IOMMU but it is not always available for various
-reasons.
+security levels available. Intel Titan Ridge added one more security level
+(usbonly). The reason for these is the fact that the connected devices can
+be DMA masters and thus read contents of the host memory without CPU and OS
+knowing about it. There are ways to prevent this by setting up an IOMMU but
+it is not always available for various reasons.
 
 The security levels are as follows:
 
@@ -52,6 +52,11 @@ The security levels are as follows:
     USB. No PCIe tunneling is done. In BIOS settings this is
     typically called *Display Port Only*.
 
+  usbonly
+    The firmware automatically creates tunnels for the USB controller and
+    Display Port in a dock. All PCIe links downstream of the dock are
+    removed.
+
 The current security level can be read from
 ``/sys/bus/thunderbolt/devices/domainX/security`` where ``domainX`` is
 the Thunderbolt domain the host controller manages. There is typically