linux-kernel - [PATCH] Documentation: Add powerpc options for spec_store_bypass

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 10 Jul 2018 12:08:36 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     corbet@....net
Cc:     keescook@...omium.org, tglx@...utronix.de, konrad.wilk@...cle.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...abs.org
Subject: [PATCH] Documentation: Add powerpc options for spec_store_bypass_disable

Document the support for spec_store_bypass_disable that was added for
powerpc in commit a048a07d7f45 ("powerpc/64s: Add support for a store
forwarding barrier at kernel entry/exit").

Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
---
 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