From patchwork Mon Jun 10 14:20:37 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Roger_Pau_Monn=C3=A9?= X-Patchwork-Id: 13692117 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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7B68AC27C65 for ; Mon, 10 Jun 2024 14:21:10 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.737297.1143529 (Exim 4.92) (envelope-from ) id 1sGftG-00009Z-RR; Mon, 10 Jun 2024 14:20:54 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 737297.1143529; Mon, 10 Jun 2024 14:20:54 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sGftG-00009S-On; Mon, 10 Jun 2024 14:20:54 +0000 Received: by outflank-mailman (input) for mailman id 737297; Mon, 10 Jun 2024 14:20:52 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sGftE-00007Q-Oc for xen-devel@lists.xenproject.org; Mon, 10 Jun 2024 14:20:52 +0000 Received: from mail-qk1-x733.google.com (mail-qk1-x733.google.com [2607:f8b0:4864:20::733]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id a35acadf-2734-11ef-90a2-e314d9c70b13; Mon, 10 Jun 2024 16:20:51 +0200 (CEST) Received: by mail-qk1-x733.google.com with SMTP id af79cd13be357-79767180a15so45375185a.1 for ; Mon, 10 Jun 2024 07:20:51 -0700 (PDT) Received: from localhost ([213.195.114.223]) by smtp.gmail.com with ESMTPSA id af79cd13be357-795758dfe3asm127231685a.105.2024.06.10.07.20.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jun 2024 07:20:48 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: a35acadf-2734-11ef-90a2-e314d9c70b13 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1718029249; x=1718634049; darn=lists.xenproject.org; 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=EmeqCABNjDotan3Y72svsvPEn7gJhsjuiG6QHhCgPvQ=; b=YvJfA12OB3sFdIw1RRotS2fex80GJdQh/gtzshnOXTHsaqPhGu3KpYWccUbMOo06RZ PF5rKb5RGDdC4R61n3IL2MZ+CbMoEhWqU1tUmeDp0WKXudkN05o5AcNRKxLy2XKkIUgu NDEPXfdUUCg3Wp/fH5KSBhWYt6PY8AtfsLxbk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718029249; x=1718634049; 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=EmeqCABNjDotan3Y72svsvPEn7gJhsjuiG6QHhCgPvQ=; b=iLMYJJPxJjepAG7OTjl31Q8V0IYwXt4W4nHBKbiTGytoZa//K4C8OFquGbEkJRK9WV TILdQTZdBdSWyb3IDSzaMm2dHF/JYJGS+1MohQNrgGab2Ouy+VyTRzu3CiccYH3tGAgo ovvtfemPIWurJnaQS6iqMF1tF88pxP6+WXVXAI3sHk/3ILl5wH51wj8AEZqOGWx8DkM/ mZRcnMku3Oc+6OI29P8AgBFusJiF/yu0tTck/yukhra39XrK+0Eyk4Ht5npAJaTfBLqC bHprzqWIY9DEer3qz0u8D2JIeQ0FaN7AqjauHL9ra+4mPKHz3HAXB6YU66Cq2Cwn4XxP EeyA== X-Gm-Message-State: AOJu0Yz6RmjOt/FSJ1cWLL+8QEc5IOn5MdHDiUe33UzynUu4dqc6udbn RiV2/zXd6Un9+TGqmbBt6db7GeIfCOCm9/wiE2WVcfjnz94Y8tkw6ILsOtqy7OdVtKK6z3wU6MM 5 X-Google-Smtp-Source: AGHT+IFVJ6qqqsqLC04Mqokc1ZPW7ysMrqYU9cIPAJV1KObi0//GhIoewHRe9csIUHpaXS5nGBBDKA== X-Received: by 2002:a05:620a:3913:b0:795:f319:e4ae with SMTP id af79cd13be357-795f319f448mr418663485a.26.1718029248808; Mon, 10 Jun 2024 07:20:48 -0700 (PDT) From: Roger Pau Monne To: xen-devel@lists.xenproject.org Cc: Roger Pau Monne , Jan Beulich , Andrew Cooper , George Dunlap , Julien Grall , Stefano Stabellini Subject: [PATCH v2 1/7] x86/smp: do not use shorthand IPI destinations in CPU hot{,un}plug contexts Date: Mon, 10 Jun 2024 16:20:37 +0200 Message-ID: <20240610142043.11924-2-roger.pau@citrix.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240610142043.11924-1-roger.pau@citrix.com> References: <20240610142043.11924-1-roger.pau@citrix.com> MIME-Version: 1.0 Due to the current rwlock logic, if the CPU calling get_cpu_maps() does so from a cpu_hotplug_{begin,done}() region the function will still return success, because a CPU taking the rwlock in read mode after having taken it in write mode is allowed. Such behavior however defeats the purpose of get_cpu_maps(), as it should always return false when called with a CPU hot{,un}plug operation is in progress. Otherwise the logic in send_IPI_mask() is wrong, as it could decide to use the shorthand even when a CPU operation is in progress. Introduce a new helper to detect whether the current caller is between a cpu_hotplug_{begin,done}() region and use it in send_IPI_mask() to restrict shorthand usage. Fixes: 5500d265a2a8 ('x86/smp: use APIC ALLBUT destination shorthand when possible') Signed-off-by: Roger Pau Monné Reviewed-by: Jan Beulich --- Changes since v1: - Modify send_IPI_mask() to detect CPU hotplug context. --- xen/arch/x86/smp.c | 2 +- xen/common/cpu.c | 5 +++++ xen/include/xen/cpu.h | 10 ++++++++++ xen/include/xen/rwlock.h | 2 ++ 4 files changed, 18 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/smp.c b/xen/arch/x86/smp.c index 7443ad20335e..04c6a0572319 100644 --- a/xen/arch/x86/smp.c +++ b/xen/arch/x86/smp.c @@ -88,7 +88,7 @@ void send_IPI_mask(const cpumask_t *mask, int vector) * the system have been accounted for. */ if ( system_state > SYS_STATE_smp_boot && - !unaccounted_cpus && !disabled_cpus && + !unaccounted_cpus && !disabled_cpus && !cpu_in_hotplug_context() && /* NB: get_cpu_maps lock requires enabled interrupts. */ local_irq_is_enabled() && (cpus_locked = get_cpu_maps()) && (park_offline_cpus || diff --git a/xen/common/cpu.c b/xen/common/cpu.c index 8709db4d2957..6e35b114c080 100644 --- a/xen/common/cpu.c +++ b/xen/common/cpu.c @@ -68,6 +68,11 @@ void cpu_hotplug_done(void) write_unlock(&cpu_add_remove_lock); } +bool cpu_in_hotplug_context(void) +{ + return rw_is_write_locked_by_me(&cpu_add_remove_lock); +} + static NOTIFIER_HEAD(cpu_chain); void __init register_cpu_notifier(struct notifier_block *nb) diff --git a/xen/include/xen/cpu.h b/xen/include/xen/cpu.h index e1d4eb59675c..6bf578675008 100644 --- a/xen/include/xen/cpu.h +++ b/xen/include/xen/cpu.h @@ -13,6 +13,16 @@ void put_cpu_maps(void); void cpu_hotplug_begin(void); void cpu_hotplug_done(void); +/* + * Returns true when the caller CPU is between a cpu_hotplug_{begin,done}() + * region. + * + * This is required to safely identify hotplug contexts, as get_cpu_maps() + * would otherwise succeed because a caller holding the lock in write mode is + * allowed to acquire the same lock in read mode. + */ +bool cpu_in_hotplug_context(void); + /* Receive notification of CPU hotplug events. */ void register_cpu_notifier(struct notifier_block *nb); diff --git a/xen/include/xen/rwlock.h b/xen/include/xen/rwlock.h index a2e98cad343e..4e7802821859 100644 --- a/xen/include/xen/rwlock.h +++ b/xen/include/xen/rwlock.h @@ -316,6 +316,8 @@ static always_inline void write_lock_irq(rwlock_t *l) #define rw_is_locked(l) _rw_is_locked(l) #define rw_is_write_locked(l) _rw_is_write_locked(l) +#define rw_is_write_locked_by_me(l) \ + lock_evaluate_nospec(_is_write_locked_by_me(atomic_read(&(l)->cnts))) typedef struct percpu_rwlock percpu_rwlock_t;