diff --git a/docs/misc/xl-disk-configuration.txt b/docs/misc/xl-disk-configuration.txt
index 11fee9a9b8..6a2118dfc4 100644
--- a/docs/misc/xl-disk-configuration.txt
+++ b/docs/misc/xl-disk-configuration.txt
@@ -217,6 +217,23 @@ If in the future the bug is fixed properly this option will then be
 silently ignored.
 
 
+discard / no-discard
+---------------
+
+Description:           Request that backend advertise discard support to frontend
+Supported values:      discard
+                       no-discard
+Mandatory:             No
+Default value:         discard
+
+An advisory setting for the backend driver, specifying whether to
+advertise discard support (TRIM, UNMAP) to the frontend.  The real
+benefit of this option is to be able to force it off rather than on.  It
+can be used to disable "hole punching" for file based backends which
+were intentionally created non-sparse to avoid fragmentation of the
+file.
+
+
 ============================================
 DEPRECATED PARAMETERS, PREFIXES AND SYNTAXES
 ============================================
diff --git a/tools/libxl/check-xl-disk-parse b/tools/libxl/check-xl-disk-parse
index 0698586cf2..1bec4ca9df 100755
--- a/tools/libxl/check-xl-disk-parse
+++ b/tools/libxl/check-xl-disk-parse
@@ -62,7 +62,8 @@ disk: {
     "removable": 0,
     "readwrite": 1,
     "is_cdrom": 0,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "True"
 }
 
 END
@@ -84,7 +85,8 @@ disk: {
     "removable": 1,
     "readwrite": 0,
     "is_cdrom": 1,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "False"
 }
 
 END
@@ -107,7 +109,8 @@ disk: {
     "removable": 0,
     "readwrite": 1,
     "is_cdrom": 0,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "True"
 }
 
 EOF
@@ -125,7 +128,8 @@ disk: {
     "removable": 1,
     "readwrite": 0,
     "is_cdrom": 1,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "False"
 }
 
 EOF
@@ -147,7 +151,8 @@ disk: {
     "removable": 1,
     "readwrite": 0,
     "is_cdrom": 1,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "False"
 }
 
 EOF
@@ -166,7 +171,8 @@ disk: {
     "removable": 0,
     "readwrite": 1,
     "is_cdrom": 0,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "True"
 }
 
 EOF
@@ -187,7 +193,8 @@ disk: {
     "removable": 0,
     "readwrite": 1,
     "is_cdrom": 0,
-    "direct_io_safe": false
+    "direct_io_safe": false,
+    "discard_enable": "True"
 }
 
 EOF
@@ -196,4 +203,63 @@ EOF
 # http://www.drbd.org/users-guide-emb/s-xen-configure-domu.html
 one 0 drbd:app01,hda,w
 
+expected <<END
+disk: {
+    "backend_domid": 0,
+    "backend_domname": null,
+    "pdev_path": "/some/disk/image.raw",
+    "vdev": "hda",
+    "backend": "unknown",
+    "format": "raw",
+    "script": null,
+    "removable": 0,
+    "readwrite": 1,
+    "is_cdrom": 0,
+    "direct_io_safe": false,
+    "discard_enable": "True"
+}
+
+END
+one 0  discard=on  vdev=hda target=/some/disk/image.raw
+one 0  discard=1   vdev=hda target=/some/disk/image.raw
+
+expected <<END
+disk: {
+    "backend_domid": 0,
+    "backend_domname": null,
+    "pdev_path": "/some/disk/image.raw",
+    "vdev": "hda",
+    "backend": "unknown",
+    "format": "raw",
+    "script": null,
+    "removable": 0,
+    "readwrite": 1,
+    "is_cdrom": 0,
+    "direct_io_safe": false,
+    "discard_enable": "False"
+}
+
+END
+one 0  discard vdev=hda target=/some/disk/image.raw
+one 0  discard vdev=hda target=/some/disk/image.raw
+
+expected <<END
+disk: {
+    "backend_domid": 0,
+    "backend_domname": null,
+    "pdev_path": "/some/disk/image.iso",
+    "vdev": "hda",
+    "backend": "unknown",
+    "format": "raw",
+    "script": null,
+    "removable": 1,
+    "readwrite": 0,
+    "is_cdrom": 1,
+    "direct_io_safe": false,
+    "discard_enable": "False"
+}
+
+END
+one 0  cdrom no-discard vdev=hda target=/some/disk/image.iso
+
 complete
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index d59ce0c288..4ea7abbad4 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2209,6 +2209,9 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
             flexarray_append(back, "direct-io-safe");
             flexarray_append(back, "1");
         }
+        flexarray_append_pair(back, "discard-enable",
+                              libxl_defbool_val(disk->discard_enable) ?
+                              "1" : "0");
 
         flexarray_append(front, "backend-id");
         flexarray_append(front, libxl__sprintf(gc, "%d", disk->backend_domid));
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 84f9c0eea8..c7aa817762 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -101,6 +101,11 @@
  */
 #define LIBXL_HAVE_DEVICE_DISK_DIRECT_IO_SAFE 1
 
+/*
+ * The libxl_device_disk has the discard_enable field.
+ */
+#define LIBXL_HAVE_LIBXL_DEVICE_DISK_DISCARD_ENABLE 1
+
 /*
  * libxl ABI compatibility
  *
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 8944686b8a..52f1aa9f21 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -417,6 +417,7 @@ libxl_device_disk = Struct("device_disk", [
     ("readwrite", integer),
     ("is_cdrom", integer),
     ("direct_io_safe", bool),
+    ("discard_enable", libxl_defbool),
     ])
 
 libxl_device_nic = Struct("device_nic", [
diff --git a/tools/libxl/libxlu_disk.c b/tools/libxl/libxlu_disk.c
index 18fe386dbe..752a2c7cdc 100644
--- a/tools/libxl/libxlu_disk.c
+++ b/tools/libxl/libxlu_disk.c
@@ -79,6 +79,7 @@ int xlu_disk_parse(XLU_Config *cfg,
         if (!disk->pdev_path || !strcmp(disk->pdev_path, ""))
             disk->format = LIBXL_DISK_FORMAT_EMPTY;
     }
+    libxl_defbool_setdefault(&disk->discard_enable, !!disk->readwrite);
 
     if (!disk->vdev) {
         xlu__disk_err(&dpc,0, "no vdev specified");
diff --git a/tools/libxl/libxlu_disk_l.l b/tools/libxl/libxlu_disk_l.l
index ba8577cc0c..1a5deb5be6 100644
--- a/tools/libxl/libxlu_disk_l.l
+++ b/tools/libxl/libxlu_disk_l.l
@@ -174,6 +174,8 @@ backendtype=[^,]*,? { STRIP(','); setbackendtype(DPC,FROMEQUALS); }
 vdev=[^,]*,?	{ STRIP(','); SAVESTRING("vdev", vdev, FROMEQUALS); }
 script=[^,]*,?	{ STRIP(','); SAVESTRING("script", script, FROMEQUALS); }
 direct-io-safe,? { DPC->disk->direct_io_safe = 1; }
+discard,?	{ libxl_defbool_set(&DPC->disk->discard_enable, true); }
+no-discard,?	{ libxl_defbool_set(&DPC->disk->discard_enable, false); }
 
  /* the target magic parameter, eats the rest of the string */
 
diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
index 1e7cea948e..6baf7fb519 100644
--- a/xen/include/public/io/blkif.h
+++ b/xen/include/public/io/blkif.h
@@ -197,6 +197,16 @@
  *
  *------------------------- Backend Device Properties -------------------------
  *
+ * discard-enable
+ *      Values:         0/1 (boolean)
+ *      Default Value:  1
+ *
+ *      This optional property, set by the toolstack, instructs the backend
+ *      to offer discard to the frontend. If the property is missing the
+ *      backend should offer discard if the backing storage actually supports
+ *      it. This optional property, set by the toolstack, requests that the
+ *      backend offer, or not offer, discard to the frontend.
+ *
  * discard-alignment
  *      Values:         <uint32_t>
  *      Default Value:  0