linux-kernel - [PATCH] Documentation/x86: Update split lock documentation

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Message-Id: <20230315225722.104607-1-tony.luck@intel.com>
Date:   Wed, 15 Mar 2023 15:57:22 -0700
From:   Tony Luck <tony.luck@...el.com>
To:     Jonathan Corbet <corbet@....net>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Tony Luck <tony.luck@...el.com>
Subject: [PATCH] Documentation/x86: Update split lock documentation

commit b041b525dab9 ("x86/split_lock: Make life miserable for split
lockers") added a delay and serialization of cplit locks. Commit
727209376f49 ("x86/split_lock: Add sysctl to control the misery mode")
provided a sysctl to turn off the misery.

Update the split lock documentation to describe the current state of
the code.

Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 Documentation/x86/buslock.rst | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/x86/buslock.rst b/Documentation/x86/buslock.rst
index 7c051e714943..31ec0ef78086 100644
--- a/Documentation/x86/buslock.rst
+++ b/Documentation/x86/buslock.rst
@@ -53,8 +53,14 @@ parameter "split_lock_detect". Here is a summary of different options:
 |off	  	   |Do nothing			|Do nothing		|
 +------------------+----------------------------+-----------------------+
 |warn		   |Kernel OOPs			|Warn once per task and |
-|(default)	   |Warn once per task and	|and continues to run.  |
-|		   |disable future checking	|			|
+|(default)	   |Warn once per task, add a	|and continues to run.  |
+|		   |delay, add synchronization	|			|
+|		   |to prevent more than one	|			|
+|		   |core from executing a	|			|
+|		   |split lock in parallel.	|			|
+|		   |sysctl split_lock_mitigate	|			|
+|		   |can be used to avoid the	|			|
+|		   |delay and synchronization	|			|
 |		   |When both features are	|			|
 |		   |supported, warn in #AC	|			|
 +------------------+----------------------------+-----------------------+
-- 
2.39.2