KVM: switch vcpu context to use SRCU

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f8bf42a..25aabd0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2933,10 +2933,9 @@
 	spin_lock(&kvm_lock);
 
 	list_for_each_entry(kvm, &vm_list, vm_list) {
-		int npages;
+		int npages, idx;
 
-		if (!down_read_trylock(&kvm->slots_lock))
-			continue;
+		idx = srcu_read_lock(&kvm->srcu);
 		spin_lock(&kvm->mmu_lock);
 		npages = kvm->arch.n_alloc_mmu_pages -
 			 kvm->arch.n_free_mmu_pages;
@@ -2949,7 +2948,7 @@
 		nr_to_scan--;
 
 		spin_unlock(&kvm->mmu_lock);
-		up_read(&kvm->slots_lock);
+		srcu_read_unlock(&kvm->srcu, idx);
 	}
 	if (kvm_freed)
 		list_move_tail(&kvm_freed->vm_list, &vm_list);