[PATCH] Documentation: Add powerpc options for spec_store_bypass_disable

---
 Documentation/admin-guide/kernel-parameters.txt | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

I tried documenting the differences between the PPC options and X86 ones in one
section, but it got quite messy, so I went with this instead. Happy to take
advice on how better to structure it if anyone has opinions.

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index efc7aa7a0670..f320c7168b04 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -4060,6 +4060,8 @@
                        This parameter controls whether the Speculative Store
                        Bypass optimization is used.

+                       On x86 the options are:
+
                        on      - Unconditionally disable Speculative Store Bypass
                        off     - Unconditionally enable Speculative Store Bypass
                        auto    - Kernel detects whether the CPU model contains an

@@ -4075,12 +4077,20 @@
                        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"

+                       On powerpc the options are:
+
+                       on,auto - On Power8 and Power9 insert a store-forwarding
+                                 barrier on kernel entry and exit. On Power7
+                                 perform a software flush on kernel entry and
+                                 exit.
+                       off     - No action.
+
+                       Not specifying this option is equivalent to
+                       spec_store_bypass_disable=auto.
+
        spia_io_base=   [HW,MTD]
        spia_fio_base=
        spia_pedr=
--

2.14.1