lkml.org 
[lkml]   [2021]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4/4] Documentation/x86: Add ratelimit in buslock.rst
Date
ratelimit is a new option in bus lock handling. Need to add it in
buslock.rst.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
Documentation/x86/buslock.rst | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/Documentation/x86/buslock.rst b/Documentation/x86/buslock.rst
index 4deaf8b82338..87ee5925cb5c 100644
--- a/Documentation/x86/buslock.rst
+++ b/Documentation/x86/buslock.rst
@@ -61,6 +61,11 @@ The kernel #AC and #DB handlers handle bus lock based on kernel parameter
| |When both features are | |
| |supported, fatal in #AC | |
+------------------+----------------------------+-----------------------+
+|ratelimit:N |Do nothing |Limit bus lock rate to |
+|(0 < N <= 1000) | |N bus locks per second |
+| | |system wide and warn on|
+| | |bus locks. |
++------------------+----------------------------+-----------------------+

Usages
======
@@ -108,3 +113,21 @@ fatal
In this case, the bus lock is not tolerated and the process is killed.

It is useful in hard real time system.
+
+ratelimit
+---------
+
+A system wide bus lock rate limit N is specified where 0 < N <= 1000.
+Less bus locks can be generated when N is smaller.
+
+This may find usage in throttling malicious processes in cloud. For
+example, a few malicious users may generate a lot of bus locks to launch
+Denial of Service (DoS) attack. By setting ratelimit, the system wide
+bus locks is rate limited by N bus locks per second and the DoS attack
+will be mitigated. The bus locks are warned so that the system
+administrator can found the malicious users and processes.
+
+Selecting a rate limit of 1000 would allow the bus to be locked for
+up to about seven million cycles each second (assuming 7000 cycles for
+each bus lock). On a 2 GHz processor that would be about 0.35% system
+impact.
--
2.31.1
\
 
 \ /
  Last update: 2021-04-19 23:51    [W:0.128 / U:0.900 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site