From 6735150b69978a9f73e3d1bab719e81a5dfafa83 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 12 May 2023 16:31:26 -0700 Subject: KVM: Use syscore_ops instead of reboot_notifier to hook restart/shutdown Use syscore_ops.shutdown to disable hardware virtualization during a reboot instead of using the dedicated reboot_notifier so that KVM disables virtualization _after_ system_state has been updated. This will allow fixing a race in KVM's handling of a forced reboot where KVM can end up enabling hardware virtualization between kernel_restart_prepare() and machine_restart(). Rename KVM's hook to match the syscore op to avoid any possible confusion from wiring up a "reboot" helper to a "shutdown" hook (neither "shutdown nor "reboot" is completely accurate as the hook handles both). Opportunistically rewrite kvm_shutdown()'s comment to make it less VMX specific, and to explain why kvm_rebooting exists. Cc: Marc Zyngier Cc: Oliver Upton Cc: James Morse Cc: Suzuki K Poulose Cc: Zenghui Yu Cc: kvmarm@lists.linux.dev Cc: Huacai Chen Cc: Aleksandar Markovic Cc: Anup Patel Cc: Atish Patra Cc: kvm-riscv@lists.infradead.org Signed-off-by: Sean Christopherson Acked-by: Marc Zyngier Message-Id: <20230512233127.804012-2-seanjc@google.com> Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index cb5c13eee193..2079d6065795 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5213,26 +5213,24 @@ static int hardware_enable_all(void) return r; } -static int kvm_reboot(struct notifier_block *notifier, unsigned long val, - void *v) +static void kvm_shutdown(void) { /* - * Some (well, at least mine) BIOSes hang on reboot if - * in vmx root mode. - * - * And Intel TXT required VMX off for all cpu when system shutdown. + * Disable hardware virtualization and set kvm_rebooting to indicate + * that KVM has asynchronously disabled hardware virtualization, i.e. + * that relevant errors and exceptions aren't entirely unexpected. + * Some flavors of hardware virtualization need to be disabled before + * transferring control to firmware (to perform shutdown/reboot), e.g. + * on x86, virtualization can block INIT interrupts, which are used by + * firmware to pull APs back under firmware control. Note, this path + * is used for both shutdown and reboot scenarios, i.e. neither name is + * 100% comprehensive. */ pr_info("kvm: exiting hardware virtualization\n"); kvm_rebooting = true; on_each_cpu(hardware_disable_nolock, NULL, 1); - return NOTIFY_OK; } -static struct notifier_block kvm_reboot_notifier = { - .notifier_call = kvm_reboot, - .priority = 0, -}; - static int kvm_suspend(void) { /* @@ -5263,6 +5261,7 @@ static void kvm_resume(void) static struct syscore_ops kvm_syscore_ops = { .suspend = kvm_suspend, .resume = kvm_resume, + .shutdown = kvm_shutdown, }; #else /* CONFIG_KVM_GENERIC_HARDWARE_ENABLING */ static int hardware_enable_all(void) @@ -5967,7 +5966,6 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) if (r) return r; - register_reboot_notifier(&kvm_reboot_notifier); register_syscore_ops(&kvm_syscore_ops); #endif @@ -6039,7 +6037,6 @@ err_cpu_kick_mask: err_vcpu_cache: #ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING unregister_syscore_ops(&kvm_syscore_ops); - unregister_reboot_notifier(&kvm_reboot_notifier); cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE); #endif return r; @@ -6065,7 +6062,6 @@ void kvm_exit(void) kvm_async_pf_deinit(); #ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING unregister_syscore_ops(&kvm_syscore_ops); - unregister_reboot_notifier(&kvm_reboot_notifier); cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE); #endif kvm_irqfd_exit(); -- cgit