From patchwork Wed Oct 7 12:20:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 11820541 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DF932618 for ; Wed, 7 Oct 2020 12:21:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB1A02080A for ; Wed, 7 Oct 2020 12:21:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="u6zdo+KS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728241AbgJGMU5 (ORCPT ); Wed, 7 Oct 2020 08:20:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728198AbgJGMUu (ORCPT ); Wed, 7 Oct 2020 08:20:50 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9721C0613D4; Wed, 7 Oct 2020 05:20:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=ZXCcrkFTyUnNhhIep8R+pz+tWqLs43q047DOUyhJ1Lk=; b=u6zdo+KSrb8nioH8uD2ma6xubX ucCpTZ8fjTVYNb/uNFIraAjwnro36cD7WdFngAmM3QGfJswDHZgvdncjP13onk5od47Bg+xVkX+BR UrgaO9gTWS/kS0TXNbobGMw5uXzsmhth/win1kMX5iOKd4L8KTjBEOEONKlL23Dm8nx59qD6Tv80g wpv113VU0ySeBHPE4BQ0XQ4KTgPgB6sT9B5FOwg5soguLjadPRHhjDgkGKVPXjdqoQbu48EE88SwP M1I19mjUdjw86dS113KnZju+DDz9HteGvAF463iYDSpqFTIzDJePCp5e4FITuQlKKR7uCgcLUCqdS y+W7ei/A==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQ8R5-0002Za-0y; Wed, 07 Oct 2020 12:20:47 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.93 #3 (Red Hat Linux)) id 1kQ8R4-004fhe-HK; Wed, 07 Oct 2020 13:20:46 +0100 From: David Woodhouse To: x86@kernel.org Cc: kvm , Thomas Gleixner , Paolo Bonzini , linux-kernel Subject: [PATCH 1/5] x86/apic: Fix x2apic enablement without interrupt remapping Date: Wed, 7 Oct 2020 13:20:42 +0100 Message-Id: <20201007122046.1113577-1-dwmw2@infradead.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <803bb6b2212e65c568c84ff6882c2aa8a0ee03d5.camel@infradead.org> References: <803bb6b2212e65c568c84ff6882c2aa8a0ee03d5.camel@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse Currently, Linux as a hypervisor guest will enable x2apic only if there are no CPUs present at boot time with an APIC ID above 255. Hotplugging a CPU later with a higher APIC ID would result in a CPU which cannot be targeted by external interrupts. Add a filter in x2apic_apic_id_valid() which can be used to prevent such CPUs from coming online, and allow x2apic to be enabled even if they are present at boot time. Fixes: ce69a784504 ("x86/apic: Enable x2APIC without interrupt remapping under KVM") Signed-off-by: David Woodhouse --- arch/x86/include/asm/apic.h | 1 + arch/x86/kernel/apic/apic.c | 14 ++++++++------ arch/x86/kernel/apic/x2apic_phys.c | 9 +++++++++ 3 files changed, 18 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 1c129abb7f09..b0fd204e0023 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -259,6 +259,7 @@ static inline u64 native_x2apic_icr_read(void) extern int x2apic_mode; extern int x2apic_phys; +extern void __init x2apic_set_max_apicid(u32 apicid); extern void __init check_x2apic(void); extern void x2apic_setup(void); static inline int x2apic_enabled(void) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index b3eef1d5c903..113f6ca7b828 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1841,20 +1841,22 @@ static __init void try_to_enable_x2apic(int remap_mode) return; if (remap_mode != IRQ_REMAP_X2APIC_MODE) { - /* IR is required if there is APIC ID > 255 even when running - * under KVM + /* + * Using X2APIC without IR is not architecturally supported + * on bare metal but may be supported in guests. */ - if (max_physical_apicid > 255 || - !x86_init.hyper.x2apic_available()) { + if (!x86_init.hyper.x2apic_available()) { pr_info("x2apic: IRQ remapping doesn't support X2APIC mode\n"); x2apic_disable(); return; } /* - * without IR all CPUs can be addressed by IOAPIC/MSI - * only in physical mode + * Without IR, all CPUs can be addressed by IOAPIC/MSI only + * in physical mode, and CPUs with an APIC ID that cannnot + * be addressed must not be brought online. */ + x2apic_set_max_apicid(255); x2apic_phys = 1; } x2apic_enable(); diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c index bc9693841353..b4b4e89c1118 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -8,6 +8,12 @@ int x2apic_phys; static struct apic apic_x2apic_phys; +static u32 x2apic_max_apicid; + +void __init x2apic_set_max_apicid(u32 apicid) +{ + x2apic_max_apicid = apicid; +} static int __init set_x2apic_phys_mode(char *arg) { @@ -98,6 +104,9 @@ static int x2apic_phys_probe(void) /* Common x2apic functions, also used by x2apic_cluster */ int x2apic_apic_id_valid(u32 apicid) { + if (x2apic_max_apicid && apicid > x2apic_max_apicid) + return 0; + return 1; }