This is a note to let you know that I've just added the patch titled
x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto
to the 6.8-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-remove-config_bhi_mitigation_auto-and-spectre_bhi-auto.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 36d4fe147c870f6d3f6602befd7ef44393a1c87a Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Wed, 10 Apr 2024 22:40:50 -0700
Subject: x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
commit 36d4fe147c870f6d3f6602befd7ef44393a1c87a upstream.
Unlike most other mitigations' "auto" options, spectre_bhi=auto only
mitigates newer systems, which is confusing and not particularly useful.
Remove it.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/412e9dc87971b622bbbaf64740ebc1f140bff343.1712813475.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 4 ----
Documentation/admin-guide/kernel-parameters.txt | 3 ---
arch/x86/Kconfig | 4 ----
arch/x86/kernel/cpu/bugs.c | 10 +---------
4 files changed, 1 insertion(+), 20 deletions(-)
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -669,10 +669,6 @@ kernel command line.
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.
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
@@ -6040,9 +6040,6 @@
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.
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2630,10 +2630,6 @@ config SPECTRE_BHI_OFF
bool "off"
help
Equivalent to setting spectre_bhi=off command line parameter.
-config SPECTRE_BHI_AUTO
- bool "auto"
- help
- Equivalent to setting spectre_bhi=auto command line parameter.
endchoice
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1624,13 +1624,10 @@ static bool __init spec_ctrl_bhi_dis(voi
enum bhi_mitigations {
BHI_MITIGATION_OFF,
BHI_MITIGATION_ON,
- BHI_MITIGATION_AUTO,
};
static enum bhi_mitigations bhi_mitigation __ro_after_init =
- IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON :
- IS_ENABLED(CONFIG_SPECTRE_BHI_OFF) ? BHI_MITIGATION_OFF :
- BHI_MITIGATION_AUTO;
+ IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON : BHI_MITIGATION_OFF;
static int __init spectre_bhi_parse_cmdline(char *str)
{
@@ -1641,8 +1638,6 @@ static int __init spectre_bhi_parse_cmdl
bhi_mitigation = BHI_MITIGATION_OFF;
else if (!strcmp(str, "on"))
bhi_mitigation = BHI_MITIGATION_ON;
- else if (!strcmp(str, "auto"))
- bhi_mitigation = BHI_MITIGATION_AUTO;
else
pr_err("Ignoring unknown spectre_bhi option (%s)", str);
@@ -1672,9 +1667,6 @@ static void __init bhi_select_mitigation
setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT);
pr_info("Spectre BHI mitigation: SW BHB clearing on vm exit\n");
- if (bhi_mitigation == BHI_MITIGATION_AUTO)
- return;
-
/* Mitigate syscalls when the mitigation is forced =on */
setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP);
pr_info("Spectre BHI mitigation: SW BHB clearing on syscall\n");
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-6.8/x86-bugs-fix-bhi-documentation.patch
queue-6.8/x86-bugs-cache-the-value-of-msr_ia32_arch_capabilities.patch
queue-6.8/x86-bugs-remove-config_bhi_mitigation_auto-and-spectre_bhi-auto.patch
queue-6.8/x86-bugs-replace-config_spectre_bhi_-on-off-with-config_mitigation_spectre_bhi.patch
queue-6.8/x86-bugs-rename-various-ia32_cap-variables-to-x86_arch_cap_msr.patch
queue-6.8/x86-bugs-clarify-that-syscall-hardening-isn-t-a-bhi-mitigation.patch
queue-6.8/x86-bugs-fix-bhi-handling-of-rrsba.patch
