KVM: arm/arm64: VGIC/ITS save/restore: protect kvm_read_guest() calls

kvm_read_guest() will eventually look up in kvm_memslots(), which requires
either to hold the kvm->slots_lock or to be inside a kvm->srcu critical
section.
In contrast to x86 and s390 we don't take the SRCU lock on every guest
exit, so we have to do it individually for each kvm_read_guest() call.
Use the newly introduced wrapper for that.

Cc: Stable <stable@vger.kernel.org> # 4.12+
Reported-by: Jan Glauber <jan.glauber@caviumnetworks.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/arm/vgic/vgic-its.c

@@ -1897,7 +1897,7 @@ static int scan_its_table(struct vgic_its *its, gpa_t base, int size, int esz,
 		int next_offset;
 		size_t byte_offset;
 
-		ret = kvm_read_guest(kvm, gpa, entry, esz);
+		ret = kvm_read_guest_lock(kvm, gpa, entry, esz);
 		if (ret)
 			return ret;
 
@@ -2267,7 +2267,7 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
 	int ret;
 
 	BUG_ON(esz > sizeof(val));
-	ret = kvm_read_guest(kvm, gpa, &val, esz);
+	ret = kvm_read_guest_lock(kvm, gpa, &val, esz);
 	if (ret)
 		return ret;
 	val = le64_to_cpu(val);

virt/kvm/arm/vgic/vgic-v3.c

@@ -344,7 +344,7 @@ int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
 	bit_nr = irq->intid % BITS_PER_BYTE;
 	ptr = pendbase + byte_offset;
 
-	ret = kvm_read_guest(kvm, ptr, &val, 1);
+	ret = kvm_read_guest_lock(kvm, ptr, &val, 1);
 	if (ret)
 		return ret;
 
@@ -397,7 +397,7 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
 		ptr = pendbase + byte_offset;
 
 		if (byte_offset != last_byte_offset) {
-			ret = kvm_read_guest(kvm, ptr, &val, 1);
+			ret = kvm_read_guest_lock(kvm, ptr, &val, 1);
 			if (ret)
 				return ret;
 			last_byte_offset = byte_offset;