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Subject[PATCH v4 2/5] cpu/speculation: Fix CPU mitigation defaults for !x86
Date
CPU speculative execution mitigations were inadvertently disabled on
non-x86 arches by the following commit:

f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n")

Fix it by replacing CONFIG_SPECULATION_MITIGATIONS with a new generic
CONFIG_CPU_MITIGATIONS option and moving the x86-specific mitigations to
a separate menu which depends on CONFIG_CPU_MITIGATIONS.

Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lkml.kernel.org/r/20240413115324.53303a68%40canb.auug.org.au
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/Kconfig | 10 ++++++++++
arch/x86/Kconfig | 15 +++------------
kernel/cpu.c | 4 ++--
3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 9f066785bb71..5c96849eb957 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -11,6 +11,16 @@ source "arch/$(SRCARCH)/Kconfig"

menu "General architecture-dependent options"

+config CPU_MITIGATIONS
+ bool "Mitigations for CPU speculative execution vulnerabilities"
+ default y
+ help
+ Say Y here to enable mitigations for CPU speculative execution
+ vulnerabilities.
+
+ If you say N, all mitigations will be disabled. You really
+ should know what you are doing to say so.
+
config ARCH_HAS_SUBPAGE_FAULTS
bool
help
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4474bf32d0a4..85a4d57bce1e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2488,17 +2488,8 @@ config PREFIX_SYMBOLS
def_bool y
depends on CALL_PADDING && !CFI_CLANG

-menuconfig SPECULATION_MITIGATIONS
- bool "Mitigations for speculative execution vulnerabilities"
- default y
- help
- Say Y here to enable options which enable mitigations for
- speculative execution hardware vulnerabilities.
-
- If you say N, all mitigations will be disabled. You really
- should know what you are doing to say so.
-
-if SPECULATION_MITIGATIONS
+menu "CPU speculative execution mitigation defaults"
+ depends on CPU_MITIGATIONS

config MITIGATION_PAGE_TABLE_ISOLATION
bool "Remove the kernel mapping in user mode"
@@ -2643,7 +2634,7 @@ config MITIGATION_SPECTRE_BHI
indirect branches.
See <file:Documentation/admin-guide/hw-vuln/spectre.rst>

-endif
+endmenu

config ARCH_HAS_ADD_PAGES
def_bool y
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 07ad53b7f119..bb0ff275fb46 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -3207,8 +3207,8 @@ enum cpu_mitigations {
};

static enum cpu_mitigations cpu_mitigations __ro_after_init =
- IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
- CPU_MITIGATIONS_OFF;
+ IS_ENABLED(CONFIG_CPU_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
+ CPU_MITIGATIONS_OFF;

static int __init mitigations_parse_cmdline(char *arg)
{
--
2.44.0

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