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 770F9C4321E for ; Wed, 30 Nov 2022 23:17:07 +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=7O99gTpkZ2vvG0zRSRJV4GouikumNhF5uURJhG+VnLk=; b=JFXGxuKcHgCNJ4 GLwGqTlUoEQkTDL7WuE5MXEnnygSSyxyIb+3EsfXf6287ZD/0sSdZ+mY3Tdbdv8Ws/CuI4uV7HvtH RXjOSodT5pnHoh18rSHJ0BcRMHNlRALCGl3nh3UMycerDABPuTznkicFF7x9Hl3Sw3ILMlO4AeC2t rOfFLVVpu6H5uQHJesIm83jwV01b6GznmeIzwZTNJo/BMonOqf+Eo147R/lEPqY++fE1bknt0D2kI tEq5daX5GrEOP2PbXjBNff6jb4Oru5XOw/2XOJEM7o5a3lBPOr8vioAeNPaQRI/OY2HHSlo/T2fWo gaF3dLkGvNhTVCoOEWKg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0WIv-00396l-KI; Wed, 30 Nov 2022 23:15:53 +0000 Received: from mail-pl1-f202.google.com ([209.85.214.202]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0WE9-0036mt-6R for linux-arm-kernel@lists.infradead.org; Wed, 30 Nov 2022 23:10:54 +0000 Received: by mail-pl1-f202.google.com with SMTP id m1-20020a170902db0100b00188eec2726cso19125986plx.18 for ; Wed, 30 Nov 2022 15:10:51 -0800 (PST) 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=/jaxWTFPxmj21+X8Hbtmuwlu7GhNr4CXW1v8XgKCn2o=; b=jQgxp+u6SHc5NMy81OYePF88zDxKuqUxtOVxluvPTQI3MEuiQG2uqtD9RQG6VmOJ8F kk/Pbv5hy6CTAGXGAAE4oRsWW1h1FNSdzY+gt8AUeNr14OcCE+UIvjb6UQ7TpiTMFIF0 izlNrD0kV5SMk0eBnY4nR4B5h0mn3eoylpGXZ25XCA4WeenN75ctGGp49AtZXHGvUS+T qZhLro5p9fp3cB2diacdo0hy8LHABjsSmVzRqwSHAFnoRTmJG580sa0oMGIlwLbpLirz qqtAn0DlcrzmZfTLixcwk1Q4OO5vUHO9P7L17dYxokTmYYn2YF9q+ofLTjNmrrQIy8bI XJdQ== 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=/jaxWTFPxmj21+X8Hbtmuwlu7GhNr4CXW1v8XgKCn2o=; b=dWJmwyZlbxkXjQZ6BJKsjcTkB+nH1CR2m6FmFFpCny208RB5FTw8lzDkhr5BHbN6I1 Q6iqL9XAp+bhQwsnaUMMccGPYj/DlWP92YPFr3wxkQHsCkwvrgxSCNoFZXX+wVcGQsT/ kS/VqiCt1dA5oL1e35m6JRNOpXFmi7/W56EdDGrOiBZqlNFx7tcVfNvOeI3JYtPaaALN gBGlykO1JySHbyCojb+eiWeciGK5ekbmwZVQx9UfTNXkBbbjLbTS/bw4Ic/ZTWfWX07L oMrWtvk60dLTFaRq/Vrj34XrT2uMN4ZyMyhDhZotZaOohrISp0bGnJwn575Ow69MoQAZ uMFA== X-Gm-Message-State: ANoB5pnYvglQTfuW+2cetc1jj0q/TjcqcDjO97BejSJEgAMU4NvzWLuk BGx3QmQtI2NcWZ4oGK8vDPQNSQH5U/s= X-Google-Smtp-Source: AA0mqf6+Bap4v8ExdEec6znsKgSVG1g77x3d69DLe55WoTiV/xIM01OoU5c9uuVoqdfTkLa+0jZkKz1t3dk= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:6904:b0:185:3f7a:50cc with SMTP id j4-20020a170902690400b001853f7a50ccmr43659852plk.99.1669849850498; Wed, 30 Nov 2022 15:10:50 -0800 (PST) Date: Wed, 30 Nov 2022 23:09:26 +0000 In-Reply-To: <20221130230934.1014142-1-seanjc@google.com> Mime-Version: 1.0 References: <20221130230934.1014142-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog Message-ID: <20221130230934.1014142-43-seanjc@google.com> Subject: [PATCH v2 42/50] KVM: Disable CPU hotplug during hardware enabling/disabling 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 , David Woodhouse , Paul Durrant 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, Yuan Yao , Cornelia Huck , Isaku Yamahata , "=?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?=" , Fabiano Rosas , Michael Ellerman , Kai Huang , Chao Gao , Thomas Gleixner X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221130_151053_297942_F7C89C61 X-CRM114-Status: GOOD ( 16.17 ) 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 when enabling/disabling hardware 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_{en,dis}able_all() is invoked on another CPU the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_{en,dis}able_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 | 11 ++++++++++- virt/kvm/kvm_main.c | 12 ++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index dad30097f0c3..d2ad383da998 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9281,7 +9281,16 @@ static inline void kvm_ops_update(struct kvm_x86_init_ops *ops) static int kvm_x86_check_processor_compatibility(void) { - struct cpuinfo_x86 *c = &cpu_data(smp_processor_id()); + int cpu = smp_processor_id(); + struct cpuinfo_x86 *c = &cpu_data(cpu); + + /* + * 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(!cpu_online(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 f26ea779710a..d985b24c423b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5098,15 +5098,26 @@ static void hardware_disable_all_nolock(void) static void hardware_disable_all(void) { + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); hardware_disable_all_nolock(); raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); } 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(), which also enables hardware if the + * usage count is non-zero. Disable CPU hotplug to avoid attempting to + * enable hardware multiple times. + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5121,6 +5132,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.584.g0f3c55d4c2-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel