From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Wed, 2 Nov 2022 23:19:05 +0000 Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> References: <20221102231911.3107438-1-seanjc@google.com> Message-ID: <20221102231911.3107438-39-seanjc@google.com> List-Id: To: kvm-riscv@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog 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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6034C4332F for ; Wed, 2 Nov 2022 23:20:29 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6205A4B875; Wed, 2 Nov 2022 19:20:29 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@google.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 2RTDbVIFeWbK; Wed, 2 Nov 2022 19:20:28 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D7BD34B87B; Wed, 2 Nov 2022 19:20:27 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4750D4B6C8 for ; Wed, 2 Nov 2022 19:20:26 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id BjcjUxWzlRxJ for ; Wed, 2 Nov 2022 19:20:25 -0400 (EDT) Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id CEAF24B86A for ; Wed, 2 Nov 2022 19:20:19 -0400 (EDT) Received: by mail-pl1-f201.google.com with SMTP id s15-20020a170902ea0f00b00187050232fcso241866plg.3 for ; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=QqNc2gbel1jInPNqFUgamY9IlriDQkvmhLgs/+APWLQZ26DgF8ww5iLxK5OkUpbYy3 HBY25YJUg8bQglW+8pK0XdmoWu5kp0V1X30MP4hvDgUq/lXrr/IjN5eYBpw2Cpmbjanr TqynEnzd9faNEz99LeseMmE1IXDN+BI4xwg7V9Sy2Mz5r4CleSP/B+U7AVSrFavYJ1Fj pLJTmPuFLhW67P7oNt/wLRQeJzFX3YhDs7A5R02nLIxeyDaFpeIL7acpvdeYKRt0I/5K OaH2yRJI3oUK/4Z+nQ16STa2tY+sAGIiXMgaJn/xhTNa56oRdIbBfXfqmK+HDZY/Eb8W RwKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=RJYG47SbmWc7Bhr2Bg0izCrL0J1XUmYBvqnXi74FfCuJ7/dZAQhtoc4yVw16+QNS+N 7U9Zfi5US2dgm3HJw06oUsMzj7Bo81o+xF8oHyXdss0hb6202H1uV9nq5fAuk8/giWgm yw0AkcleUaiQBkd1gnrLoYxKVZlMcovW+RMuTy8HkD/2P57OGDoKMK8dFm2XH31VVx+7 lRr7Tg+YU828ArbPrmrFfqcRMtyr4s18NaTs7qiGuDeNRn72jfjhJTD6Y9/obMXui8RK oEAM8Xp8K0U8RY0pn93sijoOEKjF9CfTaniihsATK5vMHare4u7rPkU8uF/ETGz01gjB v4kw== X-Gm-Message-State: ACrzQf3S7CPMgWdxkuen0WNLyUjqYxcT10XJx0eYuM2Mv3Zes2fTth4h fPRAqUf0ByHZH+2MqwAu/Xa1o4hPRWo= X-Google-Smtp-Source: AMsMyM4ko2OsoLvqzFyYKz9/I+3Jr5HBRqjQ9HRHF35ITIEOD8mTj17ITtdRiAaAjWe/b+jAZlUVnVQHbNk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:9308:b0:182:b2ba:755 with SMTP id bc8-20020a170902930800b00182b2ba0755mr27515720plb.107.1667431219005; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) Date: Wed, 2 Nov 2022 23:19:05 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-39-seanjc@google.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, David Hildenbrand , Atish Patra , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-s390@vger.kernel.org, Michael Ellerman , Chao Gao , Yuan Yao , kvmarm@lists.linux.dev, Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Isaku Yamahata , Fabiano Rosas , linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list Reply-To: Sean Christopherson List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8668A24F28 for ; Wed, 2 Nov 2022 23:20:19 +0000 (UTC) Received: by mail-pf1-f202.google.com with SMTP id bq6-20020a056a000e0600b0056bcbc6720fso6553pfb.22 for ; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=QqNc2gbel1jInPNqFUgamY9IlriDQkvmhLgs/+APWLQZ26DgF8ww5iLxK5OkUpbYy3 HBY25YJUg8bQglW+8pK0XdmoWu5kp0V1X30MP4hvDgUq/lXrr/IjN5eYBpw2Cpmbjanr TqynEnzd9faNEz99LeseMmE1IXDN+BI4xwg7V9Sy2Mz5r4CleSP/B+U7AVSrFavYJ1Fj pLJTmPuFLhW67P7oNt/wLRQeJzFX3YhDs7A5R02nLIxeyDaFpeIL7acpvdeYKRt0I/5K OaH2yRJI3oUK/4Z+nQ16STa2tY+sAGIiXMgaJn/xhTNa56oRdIbBfXfqmK+HDZY/Eb8W RwKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=zjdE2LqhB6lc/4IdUbvnisFvHbdRDWCu9Ho7e7/9xfx1o19JCqx3Gcxj4iGUJlNr6E WzroG1CibAG+IUoTNkOZsaCPc5lrk/drYyyo4rdg54z8P7rktBoFI7g07US7S6MCJAXd SdFAXBa+87OwNtxFToGI8QjGqSAd2z8Vu0rCcLe7FbWyJqsUfFLqfnN1zQxJpqmGIifL vutDD82PJMW5q+39gcOKBbrMqcdPaC8aUruJyts9OFP67k0N/Lam5bbC6IMTYHCED0Sx TXfNO1ipRejOV98dE/9y4NgYMvthJ8nHSEN/kEWSm91lZb+xI1RvScWyhjsJ2hvyCqF6 jOkA== X-Gm-Message-State: ACrzQf2qlNqm4vHhBnaRfq9VQhKWbW5bhNyp1h94UnKFmBnYlGtK6ChI D9LVACvqWtBWjGCXnAgjZCgWxAvAoHM= X-Google-Smtp-Source: AMsMyM4ko2OsoLvqzFyYKz9/I+3Jr5HBRqjQ9HRHF35ITIEOD8mTj17ITtdRiAaAjWe/b+jAZlUVnVQHbNk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:9308:b0:182:b2ba:755 with SMTP id bc8-20020a170902930800b00182b2ba0755mr27515720plb.107.1667431219005; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 2 Nov 2022 23:19:05 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-39-seanjc@google.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao Content-Type: text/plain; charset="UTF-8" Message-ID: <20221102231905.Om83Ke7BzaUbBCLhYXgAxiDjzOwK_oe5ngvq7suLOBQ@z> From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 34528C43219 for ; Wed, 2 Nov 2022 23:41:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:Reply-To:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID :References:Mime-Version:In-Reply-To:Date:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=k9zo+LoWNpRrGFge8g87uIKqnfQQJQcUd6lfox0dFpw=; b=TPwQ2VbyZxYu2M 7Eo2+hbm80Br9XoJKvSPRO/NmsA93LNw6LAdNiA0wl1RLfE1v3+hsU3m2P9vabjbYqVLvfloXkcDb Oj3lGlTggIjlRmRx4DJDBVLKEiMFz2kKsBcm4p55PqDZKX5KIjVidJw7q/5rrA+I6+LBEUKMDyMQr STIwizBoZk1qX4XmD3yKxnpQW5Rbj0JMBCzE59l4x4NwJ4YeEhc3dSM2zjMNA/l6xlpXOVyKrmzbG ukhSDSh/OLOyH9wYBUS30h/5bXqBnKBToAg2RvLe25XsEg1MyATyI+Bo3cSB0DPcBoOiXirxvD9ZY 1O/oHWiuh2e7SYYSLSQA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqNLx-00F4vu-AC; Wed, 02 Nov 2022 23:41:01 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqNGT-00F1m3-7e for linux-riscv@bombadil.infradead.org; Wed, 02 Nov 2022 23:35:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:Cc:To:From:Subject: Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To:Sender: Content-Transfer-Encoding:Content-ID:Content-Description; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=sBVXXxALa4Q7Ybd2rk3H+Cq9hQ c2YIzM0Ppm4VSOLJnvIWrhV1SY7etef4KYYyEIQZynbNh5j6y2K7AADP8HO07SN8JWAfIcyHdTN2m d8dNel8rVQCINwU3Q7/ghSrptBTOyZ1K/iw3bKXjYYDyik1vbldQeHnjEQ2Eb8IWBtpCVw0dSj1gx zrelbom+Sck6q9+IB9IM2G96789/xkRhhMVBDmK1Kp40LubbHBq+NkAtikRQpy+U37TwJ4KJOff8u sAhBzhdjS/aPIvyRi917jjKDOblqOIi4JPjMkHTO607i2+w05zMr9+TCEH8jj6IQXFgowsT9VBUEO Bbw00yAw==; Received: from mail-pl1-x649.google.com ([2607:f8b0:4864:20::649]) by casper.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqN22-005vwj-PV for linux-riscv@lists.infradead.org; Wed, 02 Nov 2022 23:20:29 +0000 Received: by mail-pl1-x649.google.com with SMTP id o7-20020a170902d4c700b001868cdac9adso221230plg.13 for ; Wed, 02 Nov 2022 16:20:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=QqNc2gbel1jInPNqFUgamY9IlriDQkvmhLgs/+APWLQZ26DgF8ww5iLxK5OkUpbYy3 HBY25YJUg8bQglW+8pK0XdmoWu5kp0V1X30MP4hvDgUq/lXrr/IjN5eYBpw2Cpmbjanr TqynEnzd9faNEz99LeseMmE1IXDN+BI4xwg7V9Sy2Mz5r4CleSP/B+U7AVSrFavYJ1Fj pLJTmPuFLhW67P7oNt/wLRQeJzFX3YhDs7A5R02nLIxeyDaFpeIL7acpvdeYKRt0I/5K OaH2yRJI3oUK/4Z+nQ16STa2tY+sAGIiXMgaJn/xhTNa56oRdIbBfXfqmK+HDZY/Eb8W RwKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=ENvrZyw+mOYBLeNbqoqGEpJfs8lR7WH4MiN4nBuR6FImDuXH6CN5ypMPknWE3lleCC YqzwWli21XAJzdiRpvp8TKn5HTNo0UVcZIufAWgf/ud0rfro5Ssek/bJ2470V3smz1ZG CoDOQajvk7kiGkQWEv/CTQCez40SgzX+qAPU0GXrzunqW/Wk2n11vXvD5pr3NV3Bu1Pu YKHmiOh87j7A0W16uy8diDsVZH8zUdh1HQNnsXwr82AvwbhjZ8YYLt5k6yKcDeTmm6ul 6Qm+32pYURsybwpgeIl+S62y3hW3hhdFG88wjCs43GIDArD30uP8cde2i9RqjuyGxgYy 9DnA== X-Gm-Message-State: ACrzQf19UpY9fK416G0DQYzqQbr3nfTDotMCEfsGaxGVsPDnttB614pS WelHXTinNrDi1XzqJuswsUN+wtKpSuk= X-Google-Smtp-Source: AMsMyM4ko2OsoLvqzFyYKz9/I+3Jr5HBRqjQ9HRHF35ITIEOD8mTj17ITtdRiAaAjWe/b+jAZlUVnVQHbNk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:9308:b0:182:b2ba:755 with SMTP id bc8-20020a170902930800b00182b2ba0755mr27515720plb.107.1667431219005; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) Date: Wed, 2 Nov 2022 23:19:05 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-39-seanjc@google.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221102_232026_874307_67B562ED X-CRM114-Status: GOOD ( 10.53 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 9739AC4332F for ; Wed, 2 Nov 2022 23:54:51 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4N2kJp0nYCz3g4Y for ; Thu, 3 Nov 2022 10:54:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20210112 header.b=QqNc2gbe; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=flex--seanjc.bounces.google.com (client-ip=2607:f8b0:4864:20::449; helo=mail-pf1-x449.google.com; envelope-from=3m_tiywykdnyk62fb48gg8d6.4gedafmphh4-56ndaklk.grd23k.gj8@flex--seanjc.bounces.google.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20210112 header.b=QqNc2gbe; dkim-atps=neutral Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4N2jY220M6z3dv1 for ; Thu, 3 Nov 2022 10:20:22 +1100 (AEDT) Received: by mail-pf1-x449.google.com with SMTP id cj8-20020a056a00298800b0056cee8a0cf8so10317pfb.9 for ; Wed, 02 Nov 2022 16:20:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=QqNc2gbel1jInPNqFUgamY9IlriDQkvmhLgs/+APWLQZ26DgF8ww5iLxK5OkUpbYy3 HBY25YJUg8bQglW+8pK0XdmoWu5kp0V1X30MP4hvDgUq/lXrr/IjN5eYBpw2Cpmbjanr TqynEnzd9faNEz99LeseMmE1IXDN+BI4xwg7V9Sy2Mz5r4CleSP/B+U7AVSrFavYJ1Fj pLJTmPuFLhW67P7oNt/wLRQeJzFX3YhDs7A5R02nLIxeyDaFpeIL7acpvdeYKRt0I/5K OaH2yRJI3oUK/4Z+nQ16STa2tY+sAGIiXMgaJn/xhTNa56oRdIbBfXfqmK+HDZY/Eb8W RwKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=vzuGE2UUHng3rlzaIHdyckwT9eKn4ED3CWrGboVbYlgcklVUTS878E+SZlwhycHhr2 2Ukn666EDRRO6coe8ufmVyQ4pso6ahiSU7TggB2TQv7rihIxQu+5Xr5i0eAu1kWDypr5 7qjlOkE4RMKkwhhu0ff3J7/d/lp5uN8mJHv+36AFOpt+gTtMCfPZUJkOabFANwXZtsrs INLynCZCIR1x21LgXkGQVawoCaSPxGxNOdJdnxUZGACTbgR+f/3MggLl5ASQVpGtZh8A e/b7ZWI52sH3dm4TBCeFFGua2Lhn42nxi66IQhNFHDDpBWHtyXSwfNM0ysVqVA5pmZmh Q/vg== X-Gm-Message-State: ACrzQf3jgeNzj8r/Hz6h19C0qYbric5HuANmnBEV9GkWc7ydkHnNcy8x FD5GmydJNvlMvmLsLxN9EfKyXbMtp04= X-Google-Smtp-Source: AMsMyM4ko2OsoLvqzFyYKz9/I+3Jr5HBRqjQ9HRHF35ITIEOD8mTj17ITtdRiAaAjWe/b+jAZlUVnVQHbNk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:9308:b0:182:b2ba:755 with SMTP id bc8-20020a170902930800b00182b2ba0755mr27515720plb.107.1667431219005; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) Date: Wed, 2 Nov 2022 23:19:05 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-39-seanjc@google.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Cc: kvm@vger.kernel.org, David Hildenbrand , Atish Patra , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-s390@vger.kernel.org, Chao Gao , Suzuki K Poulose , Yuan Yao , kvmarm@lists.linux.dev, Thomas Gleixner , Alexandru Elisei , linux-arm-kernel@lists.infradead.org, Isaku Yamahata , Fabiano Rosas , linux-mips@vger.kernel.org, Oliver Upton , James Morse , kvm-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7A4F2C433FE for ; Wed, 2 Nov 2022 23:42:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:Reply-To:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID :References:Mime-Version:In-Reply-To:Date:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tglCAty7HgvuYm+ShA13RXNCsL/Kk7ucOgjw/JwEzZU=; b=2MBNQHQyymz4Wc MO/ZOU7ifZhQ6FTdlonUsfziakAAmb/Pr+tb/I0RrrywB+q4Rr8D0v/fd7bl6HMEFduPyuKqVEe3J u4Ujw0xAj9lL+n+PWJXrTaZ0htDoO6CsiEe79LsaN4f1EPrYvOc9BtWywIQE3hI3258XFKxcg5jIt LMhtv9psdOc2w+EsKsD3WgTU1JhIkgAzCkNDjCZ5t4TSik3prem0hnttoanvhFpao0aeINLSFMURS FAMfTepDBj0UncqoUm69/K5msEwAYT79/Ok5NqcB3XyCN7nQ8HCYPnyKfbV6crqYxMdoraZk7H3CH dXnBbO9Y/rSDdmRSf/CQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqNM8-00F51D-Ga; Wed, 02 Nov 2022 23:41:13 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqNGU-00F1m3-Ba for linux-arm-kernel@bombadil.infradead.org; Wed, 02 Nov 2022 23:35:22 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:Cc:To:From:Subject: Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To:Sender: Content-Transfer-Encoding:Content-ID:Content-Description; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=sBVXXxALa4Q7Ybd2rk3H+Cq9hQ c2YIzM0Ppm4VSOLJnvIWrhV1SY7etef4KYYyEIQZynbNh5j6y2K7AADP8HO07SN8JWAfIcyHdTN2m d8dNel8rVQCINwU3Q7/ghSrptBTOyZ1K/iw3bKXjYYDyik1vbldQeHnjEQ2Eb8IWBtpCVw0dSj1gx zrelbom+Sck6q9+IB9IM2G96789/xkRhhMVBDmK1Kp40LubbHBq+NkAtikRQpy+U37TwJ4KJOff8u sAhBzhdjS/aPIvyRi917jjKDOblqOIi4JPjMkHTO607i2+w05zMr9+TCEH8jj6IQXFgowsT9VBUEO Bbw00yAw==; Received: from mail-pf1-x449.google.com ([2607:f8b0:4864:20::449]) by casper.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oqN21-005vwh-Rr for linux-arm-kernel@lists.infradead.org; Wed, 02 Nov 2022 23:20:28 +0000 Received: by mail-pf1-x449.google.com with SMTP id f189-20020a6238c6000000b0056e3400fdc0so10137pfa.10 for ; Wed, 02 Nov 2022 16:20:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=QqNc2gbel1jInPNqFUgamY9IlriDQkvmhLgs/+APWLQZ26DgF8ww5iLxK5OkUpbYy3 HBY25YJUg8bQglW+8pK0XdmoWu5kp0V1X30MP4hvDgUq/lXrr/IjN5eYBpw2Cpmbjanr TqynEnzd9faNEz99LeseMmE1IXDN+BI4xwg7V9Sy2Mz5r4CleSP/B+U7AVSrFavYJ1Fj pLJTmPuFLhW67P7oNt/wLRQeJzFX3YhDs7A5R02nLIxeyDaFpeIL7acpvdeYKRt0I/5K OaH2yRJI3oUK/4Z+nQ16STa2tY+sAGIiXMgaJn/xhTNa56oRdIbBfXfqmK+HDZY/Eb8W RwKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hGyIy/c9x7gid81AWLPwZ0ljJlv+xEg20udWYHo0hbA=; b=e+GEk7tkvVcHYb/uUAkGasSt3wO2Y5kZe7e1S5HRM+Pr8SOADUXKmqticMZ3yGOv5z aZ6lDYh917fkHKGIYIK+c3Nn7t0VFgP8R6A5Jka+efXwe8dUu6qKyAiVWLJSrsXcxwMV 2BKo4c8U4KSwv/rbtDC56N4NuLOC40CN1uTqFUJW+fp2BDvkCVsq4drAnNBeAJXLsENe w3rVvTbvBktsq0c06ttrxw0YFwO9gPE7sTh4tUQVDieQ+u9Fbqb/e6/c22CrMF1wGh51 ViSTF3zbuyYsisCGXijvmplB/JFYwWvK6Jkgnj5S0QuojXIsYpcpaZRgOV1PJ2Bt0NIK WaZA== X-Gm-Message-State: ACrzQf3kHKWAiW+G1CETQ5dGvP0glvh9ywFb0rH/rha74/4Bmq2PQfxH o+/Ygd+z7VF22kPm3pgw+oP5jpQbFPc= X-Google-Smtp-Source: AMsMyM4ko2OsoLvqzFyYKz9/I+3Jr5HBRqjQ9HRHF35ITIEOD8mTj17ITtdRiAaAjWe/b+jAZlUVnVQHbNk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:9308:b0:182:b2ba:755 with SMTP id bc8-20020a170902930800b00182b2ba0755mr27515720plb.107.1667431219005; Wed, 02 Nov 2022 16:20:19 -0700 (PDT) Date: Wed, 2 Nov 2022 23:19:05 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-39-seanjc@google.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221102_232025_944721_DDE267AA X-CRM114-Status: GOOD ( 11.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Chao Gao Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel