KVM: Convert kvm_lock to raw_spinlock

Code under this lock requires non-preemptibility. Ensure this also over
-rt by converting it to raw spinlock.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ccacf0b..b6a9963 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3587,7 +3587,7 @@
 	if (nr_to_scan == 0)
 		goto out;
 
-	spin_lock(&kvm_lock);
+	raw_spin_lock(&kvm_lock);
 
 	list_for_each_entry(kvm, &vm_list, vm_list) {
 		int idx, freed_pages;
@@ -3610,7 +3610,7 @@
 	if (kvm_freed)
 		list_move_tail(&kvm_freed->vm_list, &vm_list);
 
-	spin_unlock(&kvm_lock);
+	raw_spin_unlock(&kvm_lock);
 
 out:
 	return percpu_counter_read_positive(&kvm_total_used_mmu_pages);