The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: fe42754b94a42d08cf9501790afc25c4f6a5f631 Gitweb: https://git.kernel.org/tip/fe42754b94a42d08cf9501790afc25c4f6a5f631 Author: Sean Christopherson seanjc@google.com AuthorDate: Fri, 19 Apr 2024 17:05:54 -07:00 Committer: Borislav Petkov (AMD) bp@alien8.de CommitterDate: Thu, 25 Apr 2024 15:47:35 +02:00

cpu: Re-enable CPU mitigations by default for !X86 architectures

Rename x86's to CPU_MITIGATIONS, define it in generic code, and force it on for all architectures exception x86. A recent commit to turn mitigations off by default if SPECULATION_MITIGATIONS=n kinda sorta missed that "cpu_mitigations" is completely generic, whereas SPECULATION_MITIGATIONS is x86-specific.

Rename x86's SPECULATIVE_MITIGATIONS instead of keeping both and have it select CPU_MITIGATIONS, as having two configs for the same thing is unnecessary and confusing. This will also allow x86 to use the knob to manage mitigations that aren't strictly related to speculative execution.

Use another Kconfig to communicate to common code that CPU_MITIGATIONS is already defined instead of having x86's menu depend on the common CPU_MITIGATIONS. This allows keeping a single point of contact for all of x86's mitigations, and it's not clear that other architectures *want* to allow disabling mitigations at compile-time.

Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n") Closes: https://lkml.kernel.org/r/20240413115324.53303a68%40canb.auug.org.au 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 Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Acked-by: Josh Poimboeuf jpoimboe@kernel.org Acked-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240420000556.2645001-2-seanjc@google.com --- arch/Kconfig | 8 ++++++++ arch/x86/Kconfig | 11 ++++++----- kernel/cpu.c | 4 ++-- 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig index 65afb1d..30f7930 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -9,6 +9,14 @@ # source "arch/$(SRCARCH)/Kconfig"

+config ARCH_CONFIGURES_CPU_MITIGATIONS + bool + +if !ARCH_CONFIGURES_CPU_MITIGATIONS +config CPU_MITIGATIONS + def_bool y +endif + menu "General architecture-dependent options"

config ARCH_HAS_SUBPAGE_FAULTS diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4474bf3..619a04d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -62,6 +62,7 @@ config X86 select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU select ARCH_32BIT_OFF_T if X86_32 select ARCH_CLOCKSOURCE_INIT + select ARCH_CONFIGURES_CPU_MITIGATIONS select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 @@ -2488,17 +2489,17 @@ config PREFIX_SYMBOLS def_bool y depends on CALL_PADDING && !CFI_CLANG

-menuconfig SPECULATION_MITIGATIONS - bool "Mitigations for speculative execution vulnerabilities" +menuconfig CPU_MITIGATIONS + bool "Mitigations for CPU vulnerabilities" default y help - Say Y here to enable options which enable mitigations for - speculative execution hardware vulnerabilities. + Say Y here to enable options which enable mitigations for hardware + vulnerabilities (usually related to speculative execution).

If you say N, all mitigations will be disabled. You really should know what you are doing to say so.

-if SPECULATION_MITIGATIONS +if CPU_MITIGATIONS

config MITIGATION_PAGE_TABLE_ISOLATION bool "Remove the kernel mapping in user mode" diff --git a/kernel/cpu.c b/kernel/cpu.c index 07ad53b..bb0ff27 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) {