This is a note to let you know that I've just added the patch titled
x86/bugs: Fix BHI documentation
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-bugs-fix-bhi-documentation.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From dfe648903f42296866d79f10d03f8c85c9dfba30 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Wed, 10 Apr 2024 22:40:45 -0700
Subject: x86/bugs: Fix BHI documentation
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
commit dfe648903f42296866d79f10d03f8c85c9dfba30 upstream.
Fix up some inaccuracies in the BHI documentation.
Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob")
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Link: https://lore.kernel.org/r/8c84f7451bfe0dd08543c6082a383f390d4aa7e2.1712813475.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 15 ++++++++-------
Documentation/admin-guide/kernel-parameters.txt | 12 +++++++-----
2 files changed, 15 insertions(+), 12 deletions(-)
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -439,11 +439,11 @@ The possible values in this file are:
- System is protected by retpoline
* - BHI: BHI_DIS_S
- System is protected by BHI_DIS_S
- * - BHI: SW loop; KVM SW loop
+ * - BHI: SW loop, KVM SW loop
- System is protected by software clearing sequence
* - BHI: Syscall hardening
- Syscalls are hardened against BHI
- * - BHI: Syscall hardening; KVM: SW loop
+ * - BHI: Syscall hardening, KVM: SW loop
- System is protected from userspace attacks by syscall hardening; KVM is protected by software clearing sequence
Full mitigation might require a microcode update from the CPU
@@ -666,13 +666,14 @@ kernel command line.
of the HW BHI control and the SW BHB clearing sequence.
on
- unconditionally enable.
+ (default) Enable the HW or SW mitigation as
+ needed.
off
- unconditionally disable.
+ Disable the mitigation.
auto
- enable if hardware mitigation
- control(BHI_DIS_S) is available, otherwise
- enable alternate mitigation in KVM.
+ Enable the HW mitigation if needed, but
+ *don't* enable the SW mitigation except for KVM.
+ The system may be vulnerable.
For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3343,6 +3343,7 @@
reg_file_data_sampling=off [X86]
retbleed=off [X86]
spec_store_bypass_disable=off [X86,PPC]
+ spectre_bhi=off [X86]
spectre_v2_user=off [X86]
srbds=off [X86,INTEL]
ssbd=force-off [ARM64]
@@ -5926,11 +5927,12 @@
deployment of the HW BHI control and the SW BHB
clearing sequence.
- on - unconditionally enable.
- off - unconditionally disable.
- auto - (default) enable hardware mitigation
- (BHI_DIS_S) if available, otherwise enable
- alternate mitigation in KVM.
+ on - (default) Enable the HW or SW mitigation
+ as needed.
+ off - Disable the mitigation.
+ auto - Enable the HW mitigation if needed, but
+ *don't* enable the SW mitigation except
+ for KVM. The system may be vulnerable.
spectre_v2= [X86] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability.
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-6.6/x86-bugs-fix-bhi-documentation.patch
