From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A05CC433F5 for ; Mon, 28 Feb 2022 21:36:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230457AbiB1Vgs (ORCPT ); Mon, 28 Feb 2022 16:36:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229758AbiB1Vgr (ORCPT ); Mon, 28 Feb 2022 16:36:47 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1503F149951 for ; Mon, 28 Feb 2022 13:36:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID: Sender:Reply-To:Content-ID:Content-Description; bh=hs7WDIZJlPZyDdP2h5rMRPbPR3qYHuRMed6LHI5a8ss=; b=GlJ/SjVtqSwz7ZBzQBYfFjtI4t oKduZ6rdJMhhHYPXk/FZjjRGoyUt/m9bU2XeVvyo+7PCiQ9cHzKDSPwOeh7qlyVGB47tV88OBV6xP wPD0qCu1UmHg4H69wWBb9rfTxRLQUSriPQXHp/kQPe99mI160Zpif1cwZYRwB2H0a/q1+sK8MYSIW tqmGGFjp8MS8X0a6fl6Fef3718y1ebACIcP3Z2Fsw2KSmPBCs/XYZZiLEdZLUxKn3rrleMc1OoDtY mvOjrpgbnFsnkJhsareiajEoXsob4cDh4otmrEucLwKBfxVNtnjabWt1TJS1d1Ymrpa379Wa9cCEc c2FxUuCg==; Received: from [2601:1c0:6280:3f0::aa0b] by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nOngY-00E0nu-OX; Mon, 28 Feb 2022 21:36:03 +0000 Message-ID: <572ea830-b376-0e38-8f62-09dbd9ba9900@infradead.org> Date: Mon, 28 Feb 2022 13:35:56 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 01/10] x86/Kconfig: enable X86_X2APIC by default and improve help text Content-Language: en-US To: =?UTF-8?Q?Mateusz_Jo=c5=84czyk?= , linux-kernel@vger.kernel.org, x86@kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Yinghai Lu References: <20220228212826.27080-1-mat.jonczyk@o2.pl> <20220228212826.27080-2-mat.jonczyk@o2.pl> From: Randy Dunlap In-Reply-To: <20220228212826.27080-2-mat.jonczyk@o2.pl> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi-- On 2/28/22 13:28, Mateusz Jończyk wrote: > As many current platforms (most modern Intel CPUs and QEMU) have x2APIC > present, enable CONFIG_X86_X2APIC by default as it gives performance > and functionality benefits. Additionally, if the BIOS has already > switched APIC to x2APIC mode, but CONFIG_X86_X2APIC is disabled, the > kernel will panic in arch/x86/kernel/apic/apic.c . > > Also improve the help text, which was confusing and really did not > describe what the feature is about. > > > Signed-off-by: Mateusz Jończyk > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: Dave Hansen > Cc: x86@kernel.org > Cc: "H. Peter Anvin" > Cc: Yinghai Lu > --- > arch/x86/Kconfig | 22 +++++++++++++++++----- > 1 file changed, 17 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 9f5bd41bf660..64d760a2b81a 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -437,15 +437,27 @@ config X86_FEATURE_NAMES > If in doubt, say Y. > > config X86_X2APIC > - bool "Support x2apic" > + bool "Support CPUs with x2APIC interrupt controllers" > depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST) > + default y > help > - This enables x2apic support on CPUs that have this feature. > + x2APIC is an interrupt controller architecture, a component of which > + (the local APIC) is present in the CPU. It allows faster access to > + the local APIC and supports a larger number of CPUs in the system > + then the predecessors. than > > - This allows 32-bit apic IDs (so it can support very large systems), > - and accesses the local apic via MSRs not via mmio. > + x2APIC was introduced in Intel CPUs around 2008 and in AMD EPYC CPUs > + 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 be checked by executing CPU can be checked by executing > + cat /proc/cpuinfo | grep x2apic > > - If you don't know what to do here, say N. > + If this configuration option is disabled, the kernel will not boot on > + some platforms that have x2APIC enabled. > + > + Say N if you know that your platform does not have x2APIC. > + > + Otherwise, say Y. > > config X86_MPPARSE > bool "Enable MPS table" if ACPI -- ~Randy