From nobody Thu Dec 18 19:43:31 2025 Received: from mx-out.tlen.pl (mx-out.tlen.pl [193.222.135.175]) (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 7E6994A05 for ; Sat, 22 Mar 2025 15:46:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.222.135.175 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742658372; cv=none; b=bIVlvYMNUDQu1vcJY73nKFtS1MtXlnobfppjacGEBPxl8pTwZe0uMOr8ZWrg9CEH09dHqGGNPdxqvoWwO2ui8222VJLJjsyyM+5lgYKPzJQCPcvIJXmhP08yxAlBCvbf4GvlT4lG9UBSxPKvPxcZFXdZaMdxs/LkeZ4qQHGsh+U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742658372; c=relaxed/simple; bh=SuzvMPktzoydjCyL0FwpRFaRBIUwk4cAP6JvclOH7xw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=U4XW9v2B/S4AHIfwztViYXLwn3axI5QXh+gks2ckhXWisi9Kg2wDaMC3OCYEJvdAn0OlybWl8WFwqHZZ7NHoAl+Yjlo2NpPmmvZYvQdHvykH9O2npfcEiiczUs7EAcoI+CXIU995lWdQ4T9Jgbbc/rP05FsySfwHGByAiS3tUG4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=o2.pl; spf=pass smtp.mailfrom=o2.pl; dkim=pass (2048-bit key) header.d=o2.pl header.i=@o2.pl header.b=MzHAif0d; arc=none smtp.client-ip=193.222.135.175 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=o2.pl Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=o2.pl Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=o2.pl header.i=@o2.pl header.b="MzHAif0d" Received: (wp-smtpd smtp.tlen.pl 45669 invoked from network); 22 Mar 2025 16:46:06 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=o2.pl; s=20241105; t=1742658366; bh=RrZUUnezMD9sA4ZZ1DlOQpAlOKevEYBgM8pi3Xou/vg=; h=From:To:Cc:Subject; b=MzHAif0d8A70zpmtUSoD5/fqBHlZ8anW+VUNUxeeuAiKYzuV+etj7+tqeRcaxz6wS PMZ7dUCfgTdKo+xxlRz+uWDuMmPz2HgFg85d2HTJiU08t48uqJRZ60ZCXC7rF9SNlU q1WgjEArHzgKYKGuxrH14nlH1NOx8lzIDPOS3kLmdc3uI4fH3yH9Qsj873ssT0XwrA NKa4+QBg6BuhX2y/xNaYfFyxsYhcu8nYgwfyOX4OQdhuNQxWYFIvhqnfWgSAG0r4Na oudzYrME4w9ODhvF26L8FET6xdSkUuYnRMcgK85/qkT2VQutPm3eSzJLRHUvEDn3K0 2cyJ8Ds3FC2KA== Received: from apn-78-30-75-41.dynamic.gprs.plus.pl (HELO localhost.localdomain) (mat.jonczyk@o2.pl@[78.30.75.41]) (envelope-sender ) by smtp.tlen.pl (WP-SMTPD) with SMTP for ; 22 Mar 2025 16:46:06 +0100 From: =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , David Heidelberg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: [PATCH] x86/Kconfig: correct X86_X2APIC help text Date: Sat, 22 Mar 2025 16:45:41 +0100 Message-Id: <20250322154541.40325-1-mat.jonczyk@o2.pl> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20250321-x86_x2apic-v3-1-b0cbaa6fa338@ixit.cz> References: <20250321-x86_x2apic-v3-1-b0cbaa6fa338@ixit.cz> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-WP-MailID: 3b34c97aa0aaf5ce3c954b86151f96a9 X-WP-AV: skaner antywirusowy Poczty o2 X-WP-SPAM: NO 0000005 [Qaat] Currently, it is not true that the kernel will panic with CONFIG_X86_X2APIC= =3Dn on systems that require it; it will try to disable the APIC and run without it to at least give the user a clear warning message. See the second variant of check_x2apic() in arch/x86/kernel/apic/apic.c . Also massage some other parts of the help text. Signed-off-by: Mateusz Jo=C5=84czyk Fixes: 9232c49ff31c ("x86/Kconfig: Enable X86_X2APIC by default and improve= help text") Cc: David Heidelberg Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- This patch fixes a patch currently in tip.git master and depends on it. I have not verified recently that the kernel will work at all without CONFIG_X86_X2APIC on systems which force enable it - but it was working in 2022. --- arch/x86/Kconfig | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index e72cb7779038..ef48584c8889 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -471,14 +471,15 @@ config X86_X2APIC in 2019, but it can be disabled by the BIOS. It is also frequently emulated in virtual machines, even when the host CPU does not support it. Support in the CPU can be checked by executing - cat /proc/cpuinfo | grep x2apic + grep x2apic /proc/cpuinfo =20 - If this configuration option is disabled, the kernel will not boot on - some platforms that have x2APIC enabled. + If this configuration option is disabled, the kernel will boot with + very reduced functionality and performance on some platforms that + have x2APIC enabled. On the other hand, on hardware that does not + support x2APIC, a kernel with this option enabled will just fallback + to older APIC implementations. =20 - Say N if you know that your platform does not have x2APIC. - - Otherwise, say Y. + If in doubt, say Y. =20 config X86_POSTED_MSI bool "Enable MSI and MSI-x delivery by posted interrupts" --=20 2.25.1