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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2C1FC433EF for ; Wed, 16 Feb 2022 03:16:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344167AbiBPDQt (ORCPT ); Tue, 15 Feb 2022 22:16:49 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:59104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244696AbiBPDQp (ORCPT ); Tue, 15 Feb 2022 22:16:45 -0500 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCFCDA185; Tue, 15 Feb 2022 19:16:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644981393; x=1676517393; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=CXIRvtzJsiu2gcoHHl+uHSkuWDGrmc7HzH3aUUMVke4=; b=B1KzLwfZuCE8wqQWezao27+0XWS8eCZSUvLe15iXDwp0gaUp1uhMtx6x gjRKcgwJXwYKHAsoKO9DsQWKUbP0W1LR+kIao3vJiCNBHmGVRp+pX1hl7 1Z1n0d4z+1gavQpPc30O9M5SLsazni8xXixbQMAXtY9rab1h5rGV4wBcQ 13ZjaOs1Q5IMHhT625rFomeSvrmxXsNc/vRSvg8oa01zfONss97O4Ph01 XYddUtlZmHykcjs8g0pZjD3SdA8Yoel7u9HwXGRHotrJ018K26ZrgeDpx mms9sPN7m2quLh9gAAulpNy5Im/HSTLAyYU9s6HQWkYlw44T7kKTsrRHW A==; X-IronPort-AV: E=McAfee;i="6200,9189,10259"; a="249344574" X-IronPort-AV: E=Sophos;i="5.88,371,1635231600"; d="scan'208";a="249344574" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Feb 2022 19:16:31 -0800 X-IronPort-AV: E=Sophos;i="5.88,371,1635231600"; d="scan'208";a="773798338" Received: from hyperv-sh4.sh.intel.com ([10.239.48.22]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Feb 2022 19:16:21 -0800 From: Chao Gao To: seanjc@google.com, maz@kernel.org, kvm@vger.kernel.org, pbonzini@redhat.com, kevin.tian@intel.com, tglx@linutronix.de Cc: Chao Gao , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org Subject: [PATCH v4 6/6] KVM: Do compatibility checks on hotplugged CPUs Date: Wed, 16 Feb 2022 11:15:21 +0800 Message-Id: <20220216031528.92558-7-chao.gao@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220216031528.92558-1-chao.gao@intel.com> References: <20220216031528.92558-1-chao.gao@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At init time, KVM does compatibility checks to ensure that all online CPUs support hardware virtualization and a common set of features. But KVM uses hotplugged CPUs without such compatibility checks. On Intel CPUs, this leads to #GP if the hotplugged CPU doesn't support VMX or vmentry failure if the hotplugged CPU doesn't meet minimal feature requirements. Do compatibility checks when onlining a CPU and abort the online process if the hotplugged CPU is incompatible with online CPUs. CPU hotplug is disabled during hardware_enable_all() to prevent the corner case as shown below. A hotplugged CPU marks itself online in cpu_online_mask (1) and enables interrupt (2) before invoking callbacks registered in ONLINE section (3). So, if hardware_enable_all() is invoked on another CPU right after (2), then on_each_cpu() in hardware_enable_all() invokes hardware_enable_nolock() on the hotplugged CPU before kvm_online_cpu() is called. This makes the CPU escape from compatibility checks, which is risky. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } Keep compatibility checks at KVM init time. It can help to find incompatibility issues earlier and refuse to load arch KVM module (e.g., kvm-intel). Loosen the WARN_ON in kvm_arch_check_processor_compat so that it can be invoked from KVM's CPU hotplug callback (i.e., kvm_online_cpu). Opportunistically, add a pr_err() for setup_vmcs_config() path in vmx_check_processor_compatibility() so that each possible error path has its own error message. Convert printk(KERN_ERR ... to pr_err to please checkpatch.pl Signed-off-by: Chao Gao Reviewed-by: Sean Christopherson --- arch/x86/kvm/vmx/vmx.c | 10 ++++++---- arch/x86/kvm/x86.c | 11 +++++++++-- virt/kvm/kvm_main.c | 18 +++++++++++++++++- 3 files changed, 32 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 5e1b40e5ad87..9eb7e5dab46d 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7122,20 +7122,22 @@ static int vmx_check_processor_compatibility(void) { struct vmcs_config vmcs_conf; struct vmx_capability vmx_cap; + int cpu = smp_processor_id(); if (!this_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || !this_cpu_has(X86_FEATURE_VMX)) { - pr_err("kvm: VMX is disabled on CPU %d\n", smp_processor_id()); + pr_err("kvm: VMX is disabled on CPU %d\n", cpu); return -EIO; } - if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) + if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0) { + pr_err("kvm: failed to setup vmcs config on CPU %d\n", cpu); return -EIO; + } if (nested) nested_vmx_setup_ctls_msrs(&vmcs_conf.nested, vmx_cap.ept); if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) { - printk(KERN_ERR "kvm: CPU %d feature inconsistency!\n", - smp_processor_id()); + pr_err("kvm: CPU %d feature inconsistency!\n", cpu); return -EIO; } return 0; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ffb88f0b7265..c30e3cdb0a30 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11511,9 +11511,16 @@ void kvm_arch_hardware_unsetup(void) int kvm_arch_check_processor_compat(void) { - struct cpuinfo_x86 *c = &cpu_data(smp_processor_id()); + int cpu = smp_processor_id(); + struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM or in KVM's CPU + * hotplug callback. It ensures all online CPUs are compatible to run + * vCPUs. For other cases, compatibility checks are unnecessary or + * even problematic. Try to detect improper usages here. + */ + 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 bd60f8278867..330a5a62f043 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4855,7 +4855,11 @@ static void hardware_enable_nolock(void *caller_name) static int kvm_online_cpu(unsigned int cpu) { - int ret = 0; + int ret; + + ret = kvm_arch_check_processor_compat(); + if (ret) + return ret; raw_spin_lock(&kvm_count_lock); /* @@ -4915,6 +4919,17 @@ static int hardware_enable_all(void) { int r = 0; + /* + * During onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called. on_each_cpu() between them includes the CPU. As a result, + * hardware_enable_nolock() may get invoked before kvm_online_cpu(). + * This would enable hardware virtualization on that cpu without + * compatibility checks, which can potentially crash system or break + * running VMs. + * + * Disable CPU hotplug to prevent this case from happening. + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -4929,6 +4944,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.25.1