From nobody Wed Sep 10 02:32:49 2025 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 CC5A8C61DA4 for ; Thu, 23 Feb 2023 19:13:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232301AbjBWTNI (ORCPT ); Thu, 23 Feb 2023 14:13:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231890AbjBWTNA (ORCPT ); Thu, 23 Feb 2023 14:13:00 -0500 Received: from mail-wr1-x429.google.com (mail-wr1-x429.google.com [IPv6:2a00:1450:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D572E59E4F for ; Thu, 23 Feb 2023 11:12:14 -0800 (PST) Received: by mail-wr1-x429.google.com with SMTP id bw19so928278wrb.13 for ; Thu, 23 Feb 2023 11:12:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=OivBWw2fC0XPAqVFrKNNGqM4Zo9U9YwXqHaW8wBeEGc=; b=ZDG3NgABSuo3eKqXu8k0fCIFzS7x293O1xHnTdlbWTZzDzRsDo5w2fxICTyGIU9SZd La3hgbWjwAUViIFtj5nzdi9l286i+1BiiR8wgacSaNXsw/d9B2uf546kgw7pRzUOoU/O I9KjbX2NEBuvYhL7QbfZxgmJ52GtQy63SHB8mJdwQjIqrjEBSKFYLsgRjjr31IhELq8K +jVoVRVpaHAthXJtNr1V4FcLmQ+AKDPpCH7mcBHVUDKSMDSt9OamVRZ3xwxtubEoCSf2 oIPFuxYBjE/iDAjsJ2hW8lj2oGMrSUTAZif/uT3Llh8ahCoiI45510hGVXSicsDBQ/he p4rw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=OivBWw2fC0XPAqVFrKNNGqM4Zo9U9YwXqHaW8wBeEGc=; b=tlua53Wgv23prtyQTbfiZVe06QMipMVNal8W3oks+VfauRLqg/Jsy0WB8R+5DYb1i1 xgsMGhsYNfOBMONG/YK1MLwoI+kE1ZsJ+CviJcluOWQ1AJ7JeHzSjsUPyUJigJUYoI28 51JQ2pRFX04xVb7KVoarzxXut6qpZm/I19GgIG72sKWXnHx590ISytK8z9QpDA7rx3cm D3psf4dWS+Nz8Z98CIWEnahYVDKnaLNBjqFeJHnE3n6gmYi5USL6TwuhM6BSBdgtVPQc /grHy+d15SDAaaa01L9h/lALMlaIny7ox+Udn70UErpYWdMN1PrHb+SQl9DeKq/imHel 7+IQ== X-Gm-Message-State: AO0yUKWcVB+CPKv0WQ/feGxXhswKIh9rTRRzLORgshVwd3gDHtXie/y/ 8HGsep1+8WKbVZIOJsXMba61og== X-Google-Smtp-Source: AK7set/NLgn5F6/GhEh/DEIwsyZth9V2XRLVxbC7O+VwR1a40tCKWH8Koc0WD22GsiFjFCrm49T0DQ== X-Received: by 2002:adf:dd86:0:b0:2c7:e60:a41d with SMTP id x6-20020adfdd86000000b002c70e60a41dmr4335140wrl.61.1677179506858; Thu, 23 Feb 2023 11:11:46 -0800 (PST) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:5ee0:5af0:64bd:6198]) by smtp.gmail.com with ESMTPSA id b15-20020a5d4b8f000000b002c561805a4csm12957286wrt.45.2023.02.23.11.11.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Feb 2023 11:11:46 -0800 (PST) From: Usama Arif To: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com, brgerst@gmail.com Cc: piotrgorski@cachyos.org, oleksandr@natalenko.name, arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com, paulmck@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com, pmenzel@molgen.mpg.de, fam.zheng@bytedance.com, punit.agrawal@bytedance.com, simon.evans@bytedance.com, liangma@liangbit.com, David Woodhouse , Usama Arif Subject: [PATCH v11 04/12] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() Date: Thu, 23 Feb 2023 19:11:32 +0000 Message-Id: <20230223191140.4155012-5-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230223191140.4155012-1-usama.arif@bytedance.com> References: <20230223191140.4155012-1-usama.arif@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: David Woodhouse When bringing up a secondary CPU from do_boot_cpu(), the warm reset flag is set in CMOS and the starting IP for the trampoline written inside the BDA at 0x467. Once the CPU is running, the CMOS flag is unset and the value in the BDA cleared. To allow for parallel bringup of CPUs, add a reference count to track the number of CPUs currently bring brought up, and clear the state only when the count reaches zero. Since the RTC spinlock is required to write to the CMOS, it can be used for mutual exclusion on the refcount too. Signed-off-by: David Woodhouse Signed-off-by: Usama Arif Tested-by: Paul E. McKenney Tested-by: Kim Phillips Tested-by: Oleksandr Natalenko --- arch/x86/kernel/smpboot.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 55cad72715d9..3a793772a2aa 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -121,17 +121,20 @@ int arch_update_cpu_topology(void) return retval; } =20 + +static unsigned int smpboot_warm_reset_vector_count; + static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip) { unsigned long flags; =20 spin_lock_irqsave(&rtc_lock, flags); - CMOS_WRITE(0xa, 0xf); + if (!smpboot_warm_reset_vector_count++) { + CMOS_WRITE(0xa, 0xf); + *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =3D sta= rt_eip >> 4; + *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =3D star= t_eip & 0xf; + } spin_unlock_irqrestore(&rtc_lock, flags); - *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =3D - start_eip >> 4; - *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =3D - start_eip & 0xf; } =20 static inline void smpboot_restore_warm_reset_vector(void) @@ -143,10 +146,12 @@ static inline void smpboot_restore_warm_reset_vector(= void) * to default values. */ spin_lock_irqsave(&rtc_lock, flags); - CMOS_WRITE(0, 0xf); + if (!--smpboot_warm_reset_vector_count) { + CMOS_WRITE(0, 0xf); + *((volatile u32 *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =3D 0; + } spin_unlock_irqrestore(&rtc_lock, flags); =20 - *((volatile u32 *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =3D 0; } =20 /* --=20 2.25.1