diff --git a/src/main/scala/amba/axi4/Filter.scala b/src/main/scala/amba/axi4/Filter.scala
new file mode 100644
index 00000000..99a2e9ca
--- /dev/null
+++ b/src/main/scala/amba/axi4/Filter.scala
@@ -0,0 +1,62 @@
+// See LICENSE.SiFive for license details.
+
+package freechips.rocketchip.amba.axi4
+
+import Chisel._
+import freechips.rocketchip.config._
+import freechips.rocketchip.diplomacy._
+
+class AXI4Filter(
+  Sfilter: AXI4SlaveParameters  => Option[AXI4SlaveParameters]   = AXI4Filter.Sidentity,
+  Mfilter: AXI4MasterParameters => Option[AXI4MasterParameters]  = AXI4Filter.Midentity
+  )(implicit p: Parameters) extends LazyModule
+{
+  val node = AXI4AdapterNode(
+    slaveFn  = { sp => sp.copy(slaves = sp.slaves.flatMap { s =>
+      val out = Sfilter(s)
+      out.foreach { o => // Confirm the filter only REMOVES capability
+        o.address.foreach { a => require (s.address.map(_.contains(a)).reduce(_||_)) }
+        require (o.regionType <= s.regionType)
+        // we allow executable to be changed both ways
+        require (s.supportsWrite.contains(o.supportsWrite))
+        require (s.supportsRead .contains(o.supportsRead))
+        require (!o.interleavedId.isDefined || s.interleavedId == o.interleavedId)
+      }
+      out
+    })},
+    masterFn = { mp => mp.copy(masters = mp.masters.flatMap { m =>
+      val out = Mfilter(m)
+      out.foreach { o => require (m.id.contains(o.id)) }
+      out
+    })})
+
+  lazy val module = new LazyModuleImp(this) {
+    (node.in zip node.out) foreach { case ((in, edgeIn), (out, edgeOut)) =>
+      out <> in
+    }
+  }
+}
+
+object AXI4Filter
+{
+  def Midentity: AXI4MasterParameters => Option[AXI4MasterParameters] = { m => Some(m) }
+  def Sidentity: AXI4SlaveParameters  => Option[AXI4SlaveParameters]  = { s => Some(s) }
+  def Smask(select: AddressSet): AXI4SlaveParameters  => Option[AXI4SlaveParameters] = { s =>
+    val filtered = s.address.map(_.intersect(select)).flatten
+    val alignment = select.alignment /* alignment 0 means 'select' selected everything */
+    val maxTransfer = 1 << 30
+    val capTransfer = if (alignment == 0 || alignment > maxTransfer) maxTransfer else alignment.toInt
+    val cap = TransferSizes(1, capTransfer)
+    if (filtered.isEmpty) { None } else {
+      Some(s.copy(
+        address       = filtered,
+        supportsWrite = s.supportsWrite.intersect(cap),
+        supportsRead  = s.supportsRead .intersect(cap)))
+    }
+  }
+
+  def apply(
+    Sfilter: AXI4SlaveParameters  => Option[AXI4SlaveParameters]   = AXI4Filter.Sidentity,
+    Mfilter: AXI4MasterParameters => Option[AXI4MasterParameters]  = AXI4Filter.Midentity
+    )(implicit p: Parameters): AXI4Node = LazyModule(new AXI4Filter(Sfilter, Mfilter)).node
+}