Commit 6735150b authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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 <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: kvmarm@lists.linux.dev
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Cc: Anup Patel <anup@brainfault.org>
Cc: Atish Patra <atishp@atishpatra.org>
Cc: kvm-riscv@lists.infradead.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Message-Id: <20230512233127.804012-2-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 39428f6e

virt/kvm/kvm_main.c

+11 −15
Original line number Diff line number Diff line
@@ -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 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) 
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();