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KVM: Use syscore_ops instead of reboot_notifier to hook restart/shutdown

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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: Sean Christopherson <seanjc@google.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Message-Id: <20230512233127.804012-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-05-12 16:31:26 -07:00 committed by Paolo Bonzini
parent 39428f6ea9
commit 6735150b69
1 changed files with 11 additions and 15 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

26
virt/kvm/kvm_main.c
View file

@ -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();