diff --git a/src/main/scala/devices/tilelink/BusBlocker.scala b/src/main/scala/devices/tilelink/BusBlocker.scala
new file mode 100644
index 00000000..9403fa00
--- /dev/null
+++ b/src/main/scala/devices/tilelink/BusBlocker.scala
@@ -0,0 +1,108 @@
+// See LICENSE.SiFive for license details.
+
+package freechips.rocketchip.devices.tilelink
+
+import Chisel._
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.regmapper._
+import freechips.rocketchip.tilelink._
+import freechips.rocketchip.util._
+
+case class BusBlockerParams(
+  controlAddress:   BigInt,
+  controlBeatBytes: Int,
+  deviceBeatBytes:  Int,
+  pmpRegisters:     Int)
+{
+  val page = 4096
+  val size = (((pmpRegisters * 8) + page - 1) / page) * page
+
+  require (pmpRegisters > 0)
+  require (controlAddress > 0)
+  require (controlAddress % size == 0)
+  require (controlBeatBytes > 0 && isPow2(controlBeatBytes))
+  require (deviceBeatBytes  > 0 && isPow2(deviceBeatBytes))
+}
+
+case class DevicePMPParams(addressBits: Int)
+class DevicePMP(params: DevicePMPParams) extends GenericParameterizedBundle(params)
+{
+  require (params.addressBits > 12)
+
+  val l = UInt(width = 1) // locked
+  val a = UInt(width = 1) // LSB of A (0=disabled, 1=TOR)
+  val r = UInt(width = 1)
+  val w = UInt(width = 1)
+
+  val addr_hi = UInt(width = params.addressBits-12)
+  def address = Cat(addr_hi, UInt(0, width=12))
+
+  def fields(locked: Bool): Seq[RegField] = {
+    def field(bits: Int, reg: UInt) =
+      RegField(bits, RegReadFn(reg), RegWriteFn((wen, data) => {
+        when (wen && !locked) { reg := data }
+        Bool(true)
+      }))
+    Seq(
+      RegField(10),
+      field(params.addressBits-12, addr_hi),
+      RegField(56 - (params.addressBits-2)),
+      field(1, r),
+      field(1, w),
+      RegField(1), // x
+      field(1, a),
+      RegField(3), // a high + 2 reserved
+      field(1, l))
+  }
+}
+
+object DevicePMP
+{
+  def apply(addressBits: Int) = {
+    val out = Wire(new DevicePMP(DevicePMPParams(addressBits)))
+    out.l := UInt(0)
+    out.a := UInt(1) // TOR
+    out.r := UInt(0)
+    out.w := UInt(0)
+    out.addr_hi := ~UInt(0, width=addressBits-12)
+    out
+  }
+}
+
+class BusBlocker(params: BusBlockerParams)(implicit p: Parameters) extends TLBusBypassBase(params.deviceBeatBytes)
+{
+  val device = new SimpleDevice("bus-blocker", Seq("sifive,bus-blocker0"))
+
+  val controlNode = TLRegisterNode(
+    address   = Seq(AddressSet(params.controlAddress, params.size-1)),
+    device    = device,
+    beatBytes = params.controlBeatBytes)
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val ctl = controlNode.bundleIn
+      val in = nodeIn.bundleIn
+      val out = nodeOut.bundleOut
+    }
+
+    // We need to be able to represent +1 larger than the largest populated address
+    val addressBits = log2Ceil(nodeOut.edgesOut(0).manager.maxAddress+1+1)
+    val pmps = RegInit(Vec.fill(params.pmpRegisters) { DevicePMP(addressBits) })
+    val locks = (pmps.map(_.l) zip (UInt(0) +: pmps.map(_.l))) map { case (x, n) => x | n }
+    controlNode.regmap(0 -> (pmps zip locks).map { case (p, l) => p.fields(l(0)) }.toList.flatten)
+
+    val in = io.in(0)
+    val edge = nodeIn.edgesIn(0)
+
+    // Determine if a request is allowed
+    val needW = in.a.bits.opcode =/= TLMessages.Get
+    val needR = in.a.bits.opcode =/= TLMessages.PutFullData && in.a.bits.opcode =/= TLMessages.PutPartialData
+    val lte = Bool(false) +: pmps.map(in.a.bits.address < _.address)
+    val sel = (pmps.map(_.a) zip (lte.init zip lte.tail)) map { case (a, (l, r)) => a(0) && !l && r }
+    val ok = pmps.map(p => (p.r(0) || !needR) && (p.w(0) || !needW))
+    val allow = PriorityMux(sel :+ Bool(true), ok :+ Bool(true)) // no match => allow
+
+    bar.module.io.bypass := !allow
+  }
+}
diff --git a/src/main/scala/devices/tilelink/BusBypass.scala b/src/main/scala/devices/tilelink/BusBypass.scala
index 4bba4bd5..784d9c86 100644
--- a/src/main/scala/devices/tilelink/BusBypass.scala
+++ b/src/main/scala/devices/tilelink/BusBypass.scala
@@ -10,19 +10,23 @@ import freechips.rocketchip.tilelink._
 import freechips.rocketchip.util._
 import scala.math.min
 
-class TLBusBypass(beatBytes: Int)(implicit p: Parameters) extends LazyModule
+abstract class TLBusBypassBase(beatBytes: Int)(implicit p: Parameters) extends LazyModule
 {
-  private val nodeIn = TLInputNode()
-  private val nodeOut = TLOutputNode()
+  protected val nodeIn = TLInputNode()
+  protected val nodeOut = TLOutputNode()
   val node = NodeHandle(nodeIn, nodeOut)
 
-  private val bar = LazyModule(new TLBusBypassBar)
-  private val everything = Seq(AddressSet(0, BigInt("ffffffffffffffffffffffffffffffff", 16))) // 128-bit
-  private val error = LazyModule(new TLError(ErrorParams(everything), beatBytes))
+  protected val bar = LazyModule(new TLBusBypassBar)
+  protected val everything = Seq(AddressSet(0, BigInt("ffffffffffffffffffffffffffffffff", 16))) // 128-bit
+  protected val error = LazyModule(new TLError(ErrorParams(everything), beatBytes))
+
   bar.node := nodeIn
   error.node := bar.node
   nodeOut := bar.node
+}
 
+class TLBusBypass(beatBytes: Int)(implicit p: Parameters) extends TLBusBypassBase(beatBytes)
+{
   lazy val module = new LazyModuleImp(this) {
     val io = new Bundle {
       val in = nodeIn.bundleIn
@@ -33,7 +37,7 @@ class TLBusBypass(beatBytes: Int)(implicit p: Parameters) extends LazyModule
   }
 }
 
-private class TLBusBypassBar(implicit p: Parameters) extends LazyModule
+class TLBusBypassBar(implicit p: Parameters) extends LazyModule
 {
   // The client only sees the second slave port
   val node = TLNexusNode(