KVM: Convert kvm->requests_lock to raw_spinlock_t

The code relies on kvm->requests_lock inhibiting preemption.

Noted by Jan Kiszka.
Signed-off-by: Avi Kivity <avi@redhat.com>

include/linux/kvm_host.h

@@ -161,7 +161,7 @@ struct kvm_memslots {
 
 struct kvm {
 	spinlock_t mmu_lock;
-	spinlock_t requests_lock;
+	raw_spinlock_t requests_lock;
 	struct mutex slots_lock;
 	struct mm_struct *mm; /* userspace tied to this vm */
 	struct kvm_memslots *memslots;

virt/kvm/kvm_main.c

@@ -138,7 +138,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
 
 	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
 
-	spin_lock(&kvm->requests_lock);
+	raw_spin_lock(&kvm->requests_lock);
 	me = smp_processor_id();
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		if (test_and_set_bit(req, &vcpu->requests))
@@ -153,7 +153,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
 		smp_call_function_many(cpus, ack_flush, NULL, 1);
 	else
 		called = false;
-	spin_unlock(&kvm->requests_lock);
+	raw_spin_unlock(&kvm->requests_lock);
 	free_cpumask_var(cpus);
 	return called;
 }
@@ -409,7 +409,7 @@ static struct kvm *kvm_create_vm(void)
 	kvm->mm = current->mm;
 	atomic_inc(&kvm->mm->mm_count);
 	spin_lock_init(&kvm->mmu_lock);
-	spin_lock_init(&kvm->requests_lock);
+	raw_spin_lock_init(&kvm->requests_lock);
 	kvm_eventfd_init(kvm);
 	mutex_init(&kvm->lock);
 	mutex_init(&kvm->irq_lock);