KVM: arm64: Use kvm_write_guest_lock when init stolen time

There is a lock version kvm_write_guest. Use it to simplify code.
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20200817110728.12196-3-zhukeqian1@huawei.com

arch/arm64/kvm/pvtime.c

@@ -53,7 +53,6 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu)
 	struct pvclock_vcpu_stolen_time init_values = {};
 	struct kvm *kvm = vcpu->kvm;
 	u64 base = vcpu->arch.steal.base;
-	int idx;
 
 	if (base == GPA_INVALID)
 		return base;
@@ -63,10 +62,7 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu)
 	 * the feature enabled.
 	 */
 	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
-
-	idx = srcu_read_lock(&kvm->srcu);
-	kvm_write_guest(kvm, base, &init_values, sizeof(init_values));
-	srcu_read_unlock(&kvm->srcu, idx);
+	kvm_write_guest_lock(kvm, base, &init_values, sizeof(init_values));
 
 	return base;
 }