From nobody Sun Feb 8 16:33:21 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 734EE22A4D1; Thu, 27 Feb 2025 10:42:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740652947; cv=none; b=H5IrQn+HQkprdiiafbJP5oAEFMI8cYNwCPcr0LpDuUtI159FSJP8CLrSajDT2birtb3YmESb/MuAwtFqfz1x3+Nc3DGqGqab0lNQNYSpcF0FPumbNCIRK/mc7OUHiYS1q+8DxPAhMG+Xqt4KofQSGZvDUFtdJyfd3EHoG/JVgpQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740652947; c=relaxed/simple; bh=dalhrAXHBnIlqalGFUHzwivZCLS9GXzQfwLertdPcZI=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=UWsCHwjU2Agz2V5o8ejY1oIjmux4Sws+de3CHGgSaiiS9nhheee3+Lzwig6a4cOqUh6PwbZ22septi0AWoGy6nsLxde1HKj/j6WDo0fQ2DoJ1tuyjLHEERXeWa7Ge9fpMKvU18dvzu66C7JJCAGvcfavc+bpnE/Gd5cdAjINzpA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=phvUj2tN; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=3H/MaFea; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="phvUj2tN"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="3H/MaFea" Date: Thu, 27 Feb 2025 10:42:14 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1740652943; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mqS78blCopCtsWIZ8oaPaYcSBfzrcjYCmXJuwngzpW0=; b=phvUj2tNlNO8tF3IKYz2nct0CweJpRZA04HSbqpmNJf6h6Uu3e5Bi0OpqtiK+IVARk1keg SEmeuTvOYlXfd839/GFLCMoYJpNsno+XFMDamP1MdskARshs+98g8E6urp0ZcqSYMZjUeX pkdCY49hF33U2r94u+6vXsVIiiOnQhNxkF3l8mC1rMnMxUeVvqwsW1+iGMhTBpMv20u1Ig PvoWqTjy+aNpWAgVEFW/90C7b5lyfNfFve2z0LHr1uVTOHYKicO/DhL7w859ju1A3aamje vsDK2JBSMoLVwjuylkMgisHzksLK1jN/FiO539+tWMYT/Ht5Ut5sg9vqtRZ2Zg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1740652943; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mqS78blCopCtsWIZ8oaPaYcSBfzrcjYCmXJuwngzpW0=; b=3H/MaFeaBrqzXt4kYFdIOhKjrE+SWf6A/pH+wwZFEqbOX9qRfTuMItG4E/3tBCdtHjJVs7 3lk1S3aV0jOi2/BA== From: "tip-bot2 for Arnd Bergmann" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/cpu] x86/build: Rework CONFIG_GENERIC_CPU compiler flags Cc: Arnd Bergmann , Ingo Molnar , Linus Torvalds , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250226213714.4040853-4-arnd@kernel.org> References: <20250226213714.4040853-4-arnd@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174065294286.10177.16333107826969113374.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the x86/cpu branch of tip: Commit-ID: fc2d5cbe541032e74a66599ba843803cebbfed0e Gitweb: https://git.kernel.org/tip/fc2d5cbe541032e74a66599ba843803ce= bbfed0e Author: Arnd Bergmann AuthorDate: Wed, 26 Feb 2025 22:37:07 +01:00 Committer: Ingo Molnar CommitterDate: Thu, 27 Feb 2025 11:19:05 +01:00 x86/build: Rework CONFIG_GENERIC_CPU compiler flags Building an x86-64 kernel with CONFIG_GENERIC_CPU is documented to run on all CPUs, but the Makefile does not actually pass an -march=3D argument, instead relying on the default that was used to configure the toolchain. In many cases, gcc will be configured to -march=3Dx86-64 or -march=3Dk8 for maximum compatibility, but in other cases a distribution default may be either raised to a more recent ISA, or set to -march=3Dnative to build for the CPU used for compilation. This still works in the case of building a custom kernel for the local machine. The point where it breaks down is building a kernel for another machine that is older the the default target. Changing the default to -march=3Dx86-64 would make it work reliable, but possibly produce worse code on distros that intentionally default to a newer ISA. To allow reliably building a kernel for either the oldest x86-64 CPUs, pass the -march=3Dx86-64 flag to the compiler. This was not possible in early versions of x86-64 gcc, but works on all currently supported versions down to at least gcc-5. Signed-off-by: Arnd Bergmann Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250226213714.4040853-4-arnd@kernel.org --- arch/x86/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 5b773b3..5af3172 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -183,14 +183,14 @@ else cflags-$(CONFIG_MPSC) +=3D -march=3Dnocona cflags-$(CONFIG_MCORE2) +=3D -march=3Dcore2 cflags-$(CONFIG_MATOM) +=3D -march=3Datom - cflags-$(CONFIG_GENERIC_CPU) +=3D -mtune=3Dgeneric + cflags-$(CONFIG_GENERIC_CPU) +=3D -march=3Dx86-64 -mtune=3Dgeneric KBUILD_CFLAGS +=3D $(cflags-y) =20 rustflags-$(CONFIG_MK8) +=3D -Ctarget-cpu=3Dk8 rustflags-$(CONFIG_MPSC) +=3D -Ctarget-cpu=3Dnocona rustflags-$(CONFIG_MCORE2) +=3D -Ctarget-cpu=3Dcore2 rustflags-$(CONFIG_MATOM) +=3D -Ctarget-cpu=3Datom - rustflags-$(CONFIG_GENERIC_CPU) +=3D -Ztune-cpu=3Dgeneric + rustflags-$(CONFIG_GENERIC_CPU) +=3D -Ctarget-cpu=3Dx86-64 -Ztune-= cpu=3Dgeneric KBUILD_RUSTFLAGS +=3D $(rustflags-y) =20 KBUILD_CFLAGS +=3D -mno-red-zone