KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized

 static_key_disable_cpuslocked(): static key 'virt_spin_lock_key+0x0/0x20' used before call to jump_label_init()
 WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:161 static_key_disable_cpuslocked+0x61/0x80
 RIP: 0010:static_key_disable_cpuslocked+0x61/0x80
 Call Trace:
  static_key_disable+0x16/0x20
  start_kernel+0x192/0x4b3
  secondary_startup_64+0xa5/0xb0

Qspinlock will be choosed when dedicated pCPUs are available, however, the
static virt_spin_lock_key is set in kvm_spinlock_init() before jump_label_init()
has been called, which will result in a WARN(). This patch fixes it by delaying
the virt_spin_lock_key setup to .smp_prepare_cpus().

Reported-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Fixes: b2798ba0b876 ("KVM: X86: Choose qspinlock when dedicated physical CPUs are available")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 4ccbff63cb86a6a751a550ab5ba39f385f095902..747c61be0f51575dc5c69132455dc8b894443f1e 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -454,6 +454,13 @@ static void __init sev_map_percpu_data(void)
 }
 
 #ifdef CONFIG_SMP
+static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
+{
+       native_smp_prepare_cpus(max_cpus);
+       if (kvm_para_has_hint(KVM_HINTS_DEDICATED))
+               static_branch_disable(&virt_spin_lock_key);
+}
+
 static void __init kvm_smp_prepare_boot_cpu(void)
 {
        /*
@@ -557,6 +564,7 @@ static void __init kvm_guest_init(void)
                kvm_setup_vsyscall_timeinfo();
 
 #ifdef CONFIG_SMP
+       smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
        smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
        if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
                                      kvm_cpu_online, kvm_cpu_down_prepare) < 0)
@@ -737,10 +745,8 @@ void __init kvm_spinlock_init(void)
        if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
                return;
 
-       if (kvm_para_has_hint(KVM_HINTS_DEDICATED)) {
-               static_branch_disable(&virt_spin_lock_key);
+       if (kvm_para_has_hint(KVM_HINTS_DEDICATED))
                return;
-       }
 
        __pv_init_lock_hash();
        pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;