x86/speculation: Make "seccomp" the default mode for Speculative Store Bypass

[mirror_ubuntu-artful-kernel.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9959400653ddebfc26e9b00de79b84c5d286abec..ce24cb1e8f4614d48d1f45134347b0fceb34f215 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3953,19 +3953,27 @@
                        This parameter controls whether the Speculative Store
                        Bypass optimization is used.
 
-                       on     - Unconditionally disable Speculative Store Bypass
-                       off    - Unconditionally enable Speculative Store Bypass
-                       auto   - Kernel detects whether the CPU model contains an
-                                implementation of Speculative Store Bypass and
-                                picks the most appropriate mitigation.
-                       prctl  - Control Speculative Store Bypass per thread
-                                via prctl. Speculative Store Bypass is enabled
-                                for a process by default. The state of the control
-                                is inherited on fork.
+                       on      - Unconditionally disable Speculative Store Bypass
+                       off     - Unconditionally enable Speculative Store Bypass
+                       auto    - Kernel detects whether the CPU model contains an
+                                 implementation of Speculative Store Bypass and
+                                 picks the most appropriate mitigation. If the
+                                 CPU is not vulnerable, "off" is selected. If the
+                                 CPU is vulnerable the default mitigation is
+                                 architecture and Kconfig dependent. See below.
+                       prctl   - Control Speculative Store Bypass per thread
+                                 via prctl. Speculative Store Bypass is enabled
+                                 for a process by default. The state of the control
+                                 is inherited on fork.
+                       seccomp - Same as "prctl" above, but all seccomp threads
+                                 will disable SSB unless they explicitly opt out.
 
                        Not specifying this option is equivalent to
                        spec_store_bypass_disable=auto.
 
+                       Default mitigations:
+                       X86:    If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
+
        spia_io_base=   [HW,MTD]
        spia_fio_base=
        spia_pedr=