SPECULATION_MITIGATIONS is currently defined only for x86. As a result,
IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) is always false for other
archs. f337a6a21e2f effectively set "mitigations=off" by default on
non-x86 archs, which is not desired behavior. Jakub observed this
change when running bpf selftests on s390 and arm64.
Fix this by moving SPECULATION_MITIGATIONS to arch/Kconfig so that it is
available in all archs and thus can be used safely in kernel/cpu.c
Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n")
Cc: [email protected]
Cc: Sean Christopherson <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Daniel Sneddon <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Signed-off-by: Song Liu <[email protected]>
---
arch/Kconfig | 10 ++++++++++
arch/x86/Kconfig | 10 ----------
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 9f066785bb71..8f4af75005f8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1609,4 +1609,14 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
# strict alignment always, even with -falign-functions.
def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_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.
+
endmenu
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 39886bab943a..50c890fce5e0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2486,16 +2486,6 @@ 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
config MITIGATION_PAGE_TABLE_ISOLATION
--
2.43.0
On Mon, Apr 22, 2024, Song Liu wrote:
> SPECULATION_MITIGATIONS is currently defined only for x86. As a result,
> IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) is always false for other
> archs. f337a6a21e2f effectively set "mitigations=off" by default on
> non-x86 archs, which is not desired behavior. Jakub observed this
> change when running bpf selftests on s390 and arm64.
>
> Fix this by moving SPECULATION_MITIGATIONS to arch/Kconfig so that it is
> available in all archs and thus can be used safely in kernel/cpu.c
Yeah, it's a known issue that we've been slow to fix because we've haven't come
to an agreement on exactly what the Kconfig should look like[1], though there's
general consensus to add CPU_MITIGATIONS in common code[2][3].
I'll poke Josh's thread and make sure a fix gets into rc6.
[1] https://lore.kernel.org/all/[email protected]
[2] https://lore.kernel.org/all/[email protected]
[3] https://lore.kernel.org/all/9d3c997264829d0e2b28718222724ae8f9e7d8b4.1713559768.git.jpoimboe@kernel.org