[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <450b5f4ffe891a8cc9736ec52b0c6f225bab3f4b.1719381528.git.jpoimboe@kernel.org>
Date: Tue, 25 Jun 2024 23:02:01 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Peter Zijlstra <peterz@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Sean Christopherson <seanjc@...gle.com>,
Andrew Cooper <andrew.cooper3@...rix.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Nikolay Borisov <nik.borisov@...e.com>,
KP Singh <kpsingh@...nel.org>,
Waiman Long <longman@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Ingo Molnar <mingo@...nel.org>
Subject: [PATCH v6 2/3] x86/bugs: Remove duplicate Spectre cmdline option descriptions
Duplicating the documentation of all the Spectre kernel cmdline options
in two separate files is unwieldy and error-prone. Instead just add a
reference to kernel-parameters.txt from spectre.rst.
Reviewed-by: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 86 +++----------------
1 file changed, 10 insertions(+), 76 deletions(-)
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 25a04cda4c2c..132e0bc6007e 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -592,85 +592,19 @@ Spectre variant 2
Mitigation control on the kernel command line
---------------------------------------------
-Spectre variant 2 mitigation can be disabled or force enabled at the
-kernel command line.
+In general the kernel selects reasonable default mitigations for the
+current CPU.
- nospectre_v1
+Spectre default mitigations can be disabled or changed at the kernel
+command line with the following options:
- [X86,PPC] Disable mitigations for Spectre Variant 1
- (bounds check bypass). With this option data leaks are
- possible in the system.
+ - nospectre_v1
+ - nospectre_v2
+ - spectre_v2={option}
+ - spectre_v2_user={option}
+ - spectre_bhi={option}
- nospectre_v2
-
- [X86] Disable all mitigations for the Spectre variant 2
- (indirect branch prediction) vulnerability. System may
- allow data leaks with this option, which is equivalent
- to spectre_v2=off.
-
-
- spectre_v2=
-
- [X86] Control mitigation of Spectre variant 2
- (indirect branch speculation) vulnerability.
- The default operation protects the kernel from
- user space attacks.
-
- on
- unconditionally enable, implies
- spectre_v2_user=on
- off
- unconditionally disable, implies
- spectre_v2_user=off
- auto
- kernel detects whether your CPU model is
- vulnerable
-
- Selecting 'on' will, and 'auto' may, choose a
- mitigation method at run time according to the
- CPU, the available microcode, the setting of the
- CONFIG_MITIGATION_RETPOLINE configuration option,
- and the compiler with which the kernel was built.
-
- Selecting 'on' will also enable the mitigation
- against user space to user space task attacks.
-
- Selecting 'off' will disable both the kernel and
- the user space protections.
-
- Specific mitigations can also be selected manually:
-
- retpoline auto pick between generic,lfence
- retpoline,generic Retpolines
- retpoline,lfence LFENCE; indirect branch
- retpoline,amd alias for retpoline,lfence
- eibrs Enhanced/Auto IBRS
- eibrs,retpoline Enhanced/Auto IBRS + Retpolines
- eibrs,lfence Enhanced/Auto IBRS + LFENCE
- ibrs use IBRS to protect kernel
-
- Not specifying this option is equivalent to
- spectre_v2=auto.
-
- In general the kernel by default selects
- reasonable mitigations for the current CPU. To
- disable Spectre variant 2 mitigations, boot with
- spectre_v2=off. Spectre variant 1 mitigations
- cannot be disabled.
-
- spectre_bhi=
-
- [X86] Control mitigation of Branch History Injection
- (BHI) vulnerability. This setting affects the deployment
- of the HW BHI control and the SW BHB clearing sequence.
-
- on
- (default) Enable the HW or SW mitigation as
- needed.
- off
- Disable the mitigation.
-
-For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
+For more details on the available options, refer to Documentation/admin-guide/kernel-parameters.txt
Mitigation selection guide
--------------------------
--
2.45.1
Powered by blists - more mailing lists