linux-kernel - [tip: x86/kconfig] x86/kbuild/64: Test for the availability of the -mtune=native compiler flag

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Message-ID: <174368720454.30396.11966787075140474975.tip-bot2@tip-bot2>
Date: Thu, 03 Apr 2025 13:33:24 -0000
From: "tip-bot2 for Ingo Molnar" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Stephen Rothwell <sfr@...b.auug.org.au>, Ingo Molnar <mingo@...nel.org>,
 Tor Vic <torvic9@...lbox.org>, Andy Lutomirski <luto@...nel.org>,
 Brian Gerst <brgerst@...il.com>, Juergen Gross <jgross@...e.com>,
 "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>,
 Josh Poimboeuf <jpoimboe@...hat.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/kconfig] x86/kbuild/64: Test for the availability of the
 -mtune=native compiler flag

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

Commit-ID:     01412081863aa81db47423d5719f2726d2a00a32
Gitweb:        https://git.kernel.org/tip/01412081863aa81db47423d5719f2726d2a00a32
Author:        Ingo Molnar <mingo@...nel.org>
AuthorDate:    Mon, 24 Mar 2025 08:05:19 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 25 Mar 2025 08:24:06 +01:00

x86/kbuild/64: Test for the availability of the -mtune=native compiler flag

Stephen reported this build failure when cross-compiling:

  cc1: error: bad value 'native' for '-march=' switch

Test for the availability of the -march=native flag.

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Stephen Rothwell <sfr@...b.auug.org.au> # build test
Cc: Tor Vic <torvic9@...lbox.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/20250324172723.49fb0416@canb.auug.org.au
---
 arch/x86/Kconfig.cpu | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 9d108a5..87bede9 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -245,10 +245,14 @@ config MATOM
 
 endchoice
 
+config CC_HAS_MARCH_NATIVE
+	# This flag might not be available in cross-compilers:
+	def_bool $(cc-option, -march=native)
+
 config X86_NATIVE_CPU
 	bool "Build and optimize for local/native CPU"
 	depends on X86_64
-	default n
+	depends on CC_HAS_MARCH_NATIVE
 	help
 	  Optimize for the current CPU used to compile the kernel.
 	  Use this option if you intend to build the kernel for your