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Wed, 02 Nov 2022 16:20:17 -0700 (PDT) Date: Wed, 2 Nov 2022 23:19:04 +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: <20221102231911.3107438-38-seanjc@google.com> Subject: [PATCH 37/44] KVM: Rename and move CPUHP_AP_KVM_STARTING to ONLINE section 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 The CPU STARTING section doesn't allow callbacks to fail. Move KVM's hotplug callback to ONLINE section so that it can abort onlining a CPU in certain cases to avoid potentially breaking VMs running on existing CPUs. For example, when KVM fails to enable hardware virtualization on the hotplugged CPU. Place KVM's hotplug state before CPUHP_AP_SCHED_WAIT_EMPTY as it ensures when offlining a CPU, all user tasks and non-pinned kernel tasks have left the CPU, i.e. there cannot be a vCPU task around. So, it is safe for KVM's CPU offline callback to disable hardware virtualization at that point. Likewise, KVM's online callback can enable hardware virtualization before any vCPU task gets a chance to run on hotplugged CPUs. Rename KVM's CPU hotplug callbacks accordingly. Suggested-by: Thomas Gleixner Signed-off-by: Chao Gao Reviewed-by: Sean Christopherson Signed-off-by: Isaku Yamahata Reviewed-by: Yuan Yao Signed-off-by: Sean Christopherson --- include/linux/cpuhotplug.h | 2 +- virt/kvm/kvm_main.c | 30 ++++++++++++++++++++++-------- 2 files changed, 23 insertions(+), 9 deletions(-) diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 7337414e4947..de45be38dd27 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -185,7 +185,6 @@ enum cpuhp_state { CPUHP_AP_CSKY_TIMER_STARTING, CPUHP_AP_TI_GP_TIMER_STARTING, CPUHP_AP_HYPERV_TIMER_STARTING, - CPUHP_AP_KVM_STARTING, /* Must be the last timer callback */ CPUHP_AP_DUMMY_TIMER_STARTING, CPUHP_AP_ARM_XEN_STARTING, @@ -200,6 +199,7 @@ enum cpuhp_state { /* Online section invoked on the hotplugged CPU from the hotplug thread */ CPUHP_AP_ONLINE_IDLE, + CPUHP_AP_KVM_ONLINE, CPUHP_AP_SCHED_WAIT_EMPTY, CPUHP_AP_SMPBOOT_THREADS, CPUHP_AP_X86_VDSO_VMA_ONLINE, diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index dd13af9f06d5..fd9e39c85549 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5026,13 +5026,27 @@ static void hardware_enable_nolock(void *junk) } } -static int kvm_starting_cpu(unsigned int cpu) +static int kvm_online_cpu(unsigned int cpu) { + int ret = 0; + raw_spin_lock(&kvm_count_lock); - if (kvm_usage_count) + /* + * Abort the CPU online process if hardware virtualization cannot + * be enabled. Otherwise running VMs would encounter unrecoverable + * errors when scheduled to this CPU. + */ + if (kvm_usage_count) { + WARN_ON_ONCE(atomic_read(&hardware_enable_failed)); + hardware_enable_nolock(NULL); + if (atomic_read(&hardware_enable_failed)) { + atomic_set(&hardware_enable_failed, 0); + ret = -EIO; + } + } raw_spin_unlock(&kvm_count_lock); - return 0; + return ret; } static void hardware_disable_nolock(void *junk) @@ -5045,7 +5059,7 @@ static void hardware_disable_nolock(void *junk) kvm_arch_hardware_disable(); } -static int kvm_dying_cpu(unsigned int cpu) +static int kvm_offline_cpu(unsigned int cpu) { raw_spin_lock(&kvm_count_lock); if (kvm_usage_count) @@ -5822,8 +5836,8 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) return -ENOMEM; - r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_STARTING, "kvm/cpu:starting", - kvm_starting_cpu, kvm_dying_cpu); + r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_ONLINE, "kvm/cpu:online", + kvm_online_cpu, kvm_offline_cpu); if (r) goto out_free_2; register_reboot_notifier(&kvm_reboot_notifier); @@ -5897,7 +5911,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) kmem_cache_destroy(kvm_vcpu_cache); out_free_3: unregister_reboot_notifier(&kvm_reboot_notifier); - cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING); + cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE); out_free_2: free_cpumask_var(cpus_hardware_enabled); return r; @@ -5923,7 +5937,7 @@ void kvm_exit(void) kvm_async_pf_deinit(); unregister_syscore_ops(&kvm_syscore_ops); unregister_reboot_notifier(&kvm_reboot_notifier); - cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING); + cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE); on_each_cpu(hardware_disable_nolock, NULL, 1); kvm_irqfd_exit(); free_cpumask_var(cpus_hardware_enabled); -- 2.38.1.431.g37b22c650d-goog