Add a generic Kconfig, CPU_MITIGATIONS, to control whether or not CPU mitigations are enabled by default, and force it on for all architectures except x86. A recent commit to turn mitigations off by default if SPECULATION_MITIGATIONS=n kinda sorta missed that "cpu_mitigations" is completely generic, where as SPECULATION_MITIGATIONS is x86 specific. Alternatively, SPECULATION_MITIGATIONS could simply be defined in common code, but that creates weirdness for x86 because SPECULATION_MITIGATIONS ends up being defined twice, and the default behavior would likely depend on the arbitrary include order (if the two definitions diverged). Ideally, CPU_MITIGATIONS would be unconditionally on by default for all architectures, and manually turned off, but there is no way to unselect a Kconfig. Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Reported-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Closes: https://lkml.kernel.org/r/20240413115324.53303a68%40canb.auug.org.au Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/Kconfig | 1 + drivers/base/Kconfig | 3 +++ kernel/cpu.c | 4 ++-- 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4474bf32d0a4..a0eca6313276 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2490,6 +2490,7 @@ config PREFIX_SYMBOLS menuconfig SPECULATION_MITIGATIONS bool "Mitigations for speculative execution vulnerabilities" + select CPU_MITIGATIONS default y help Say Y here to enable options which enable mitigations for diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 2b8fd6bb7da0..dab19f15fa57 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -191,6 +191,9 @@ config GENERIC_CPU_AUTOPROBE config GENERIC_CPU_VULNERABILITIES bool +config CPU_MITIGATIONS + def_bool !X86 + config SOC_BUS bool select GLOB 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) { -- 2.44.0.683.g7961c838ac-goog
