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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: f337a6a21e ("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
This commit is contained in:
Sean Christopherson 2024-04-19 17:05:54 -07:00 committed by Borislav Petkov (AMD)
parent a0a8d15a79
commit fe42754b94
3 changed files with 16 additions and 7 deletions
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8
arch/Kconfig
View File

@ -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

11
arch/x86/Kconfig
View File

@ -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"

4
kernel/cpu.c
View File

@ -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)
{