linux-kernel - [PATCH] arch/Kconfig: Move SPECULATION

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Date: Mon, 22 Apr 2024 21:55:48 -0700
From: Song Liu <song@...nel.org>
To: linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: kernel-team@...a.com,
	Song Liu <song@...nel.org>,
	stable@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH] arch/Kconfig: Move SPECULATION_MITIGATIONS to arch/Kconfig

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: stable@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Daniel Sneddon <daniel.sneddon@...ux.intel.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Song Liu <song@...nel.org>
---
 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