libxl: Add "grant_usage" parameter for virtio disk devices

Allow administrators to control whether Xen grant mappings for
the virtio disk devices should be used. By default (when new
parameter is not specified), the existing behavior is retained
(we enable grants if backend-domid != 0).

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

docs/man/xl-disk-configuration.5.pod.in

@@ -406,6 +406,30 @@ Virtio frontend driver (virtio-blk) to be used. Please note, the virtual
 device (vdev) is not passed to the guest in that case, but it still must be
 specified for the internal purposes.
 
+=item B<grant_usage=BOOLEAN>
+
+=over 4
+
+=item Description
+
+Specifies the usage of Xen grants for accessing guest memory. Only applicable
+to specification "virtio".
+
+=item Supported values
+
+1, 0
+
+=item Mandatory
+
+No
+
+=item Default value
+
+If this option is missing, then the default grant setting will be used,
+i.e. "grant_usage=1" if backend-domid != 0 or "grant_usage=0" otherwise.
+
+=back
+
 =back
 
 =head1 COLO Parameters

tools/golang/xenlight/helpers.gen.go

@@ -1885,6 +1885,9 @@ x.ActiveDisk = C.GoString(xc.active_disk)
 x.HiddenDisk = C.GoString(xc.hidden_disk)
 if err := x.Trusted.fromC(&xc.trusted);err != nil {
 return fmt.Errorf("converting field Trusted: %v", err)
+}
+if err := x.GrantUsage.fromC(&xc.grant_usage);err != nil {
+return fmt.Errorf("converting field GrantUsage: %v", err)
 }
 
  return nil}
@@ -1933,6 +1936,9 @@ if x.HiddenDisk != "" {
 xc.hidden_disk = C.CString(x.HiddenDisk)}
 if err := x.Trusted.toC(&xc.trusted); err != nil {
 return fmt.Errorf("converting field Trusted: %v", err)
+}
+if err := x.GrantUsage.toC(&xc.grant_usage); err != nil {
+return fmt.Errorf("converting field GrantUsage: %v", err)
 }
 
  return nil

tools/golang/xenlight/types.gen.go

@@ -741,6 +741,7 @@ ColoExport string
 ActiveDisk string
 HiddenDisk string
 Trusted Defbool
+GrantUsage Defbool
 }
 
 type DeviceNic struct {

tools/include/libxl.h

@@ -578,6 +578,13 @@
  */
 #define LIBXL_HAVE_DEVICE_DISK_SPECIFICATION 1
 
+/*
+ * LIBXL_HAVE_DISK_GRANT_USAGE indicates that the libxl_device_disk
+ * has 'grant_usage' field to specify the usage of Xen grants for
+ * the specification 'virtio'.
+ */
+#define LIBXL_HAVE_DISK_GRANT_USAGE 1
+
 /*
  * LIBXL_HAVE_CONSOLE_ADD_XENSTORE indicates presence of the function
  * libxl_console_add_xenstore() in libxl.

tools/libs/light/libxl_arm.c

@@ -1372,12 +1372,12 @@ next_resize:
             libxl_device_disk *disk = &d_config->disks[i];
 
             if (disk->specification == LIBXL_DISK_SPECIFICATION_VIRTIO) {
-                if (disk->backend_domid != LIBXL_TOOLSTACK_DOMID)
+                if (libxl_defbool_val(disk->grant_usage))
                     iommu_needed = true;
 
                 FDT( make_virtio_mmio_node(gc, fdt, disk->base, disk->irq,
                                            disk->backend_domid,
-                                           disk->backend_domid != LIBXL_TOOLSTACK_DOMID) );
+                                           libxl_defbool_val(disk->grant_usage)) );
             }
         }
 

tools/libs/light/libxl_disk.c

@@ -183,6 +183,9 @@ static int libxl__device_disk_setdefault(libxl__gc *gc, uint32_t domid,
             return ERROR_INVAL;
         }
         disk->transport = LIBXL_DISK_TRANSPORT_MMIO;
+
+        libxl_defbool_setdefault(&disk->grant_usage,
+                                 disk->backend_domid != LIBXL_TOOLSTACK_DOMID);
     }
 
     if (hotplug && disk->specification == LIBXL_DISK_SPECIFICATION_VIRTIO) {
@@ -468,6 +471,8 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
             flexarray_append(back, libxl__device_disk_string_of_transport(disk->transport));
             flexarray_append_pair(back, "base", GCSPRINTF("%"PRIu64, disk->base));
             flexarray_append_pair(back, "irq", GCSPRINTF("%u", disk->irq));
+            flexarray_append_pair(back, "grant_usage",
+                                  libxl_defbool_val(disk->grant_usage) ? "1" : "0");
         }
 
         flexarray_append(front, "backend-id");
@@ -662,6 +667,14 @@ static int libxl__disk_from_xenstore(libxl__gc *gc, const char *libxl_path,
             goto cleanup;
         }
         disk->irq = strtoul(tmp, NULL, 10);
+
+        tmp = libxl__xs_read(gc, XBT_NULL,
+                             GCSPRINTF("%s/grant_usage", libxl_path));
+        if (!tmp)
+            libxl_defbool_set(&disk->grant_usage,
+                              disk->backend_domid != LIBXL_TOOLSTACK_DOMID);
+        else
+            libxl_defbool_set(&disk->grant_usage, strtoul(tmp, NULL, 0));
     }
 
     disk->vdev = xs_read(ctx->xsh, XBT_NULL,

tools/libs/light/libxl_types.idl

@@ -803,6 +803,7 @@ libxl_device_disk = Struct("device_disk", [
     ("active_disk", string),
     ("hidden_disk", string),
     ("trusted", libxl_defbool),
+    ("grant_usage", libxl_defbool),
     ])
 
 libxl_device_nic = Struct("device_nic", [

tools/libs/util/libxlu_disk_l.h

@@ -3,9 +3,12 @@
 #define xlu__disk_yyIN_HEADER 1
 
 #line 5 "libxlu_disk_l.h"
+#line 31 "libxlu_disk_l.l"
 #define _GNU_SOURCE
 
-#line 8 "libxlu_disk_l.h"
+
+
+#line 11 "libxlu_disk_l.h"
 
 #define  YY_INT_ALIGNED short int
 
@@ -694,8 +697,8 @@ extern int yylex (yyscan_t yyscanner);
 #undef yyTABLES_NAME
 #endif
 
-#line 300 "libxlu_disk_l.l"
+#line 306 "libxlu_disk_l.l"
 
-#line 699 "libxlu_disk_l.h"
+#line 702 "libxlu_disk_l.h"
 #undef xlu__disk_yyIN_HEADER
 #endif /* xlu__disk_yyHEADER_H */

tools/libs/util/libxlu_disk_l.l

@@ -220,6 +220,9 @@ hidden-disk=[^,]*,?	{ STRIP(','); SAVESTRING("hidden-disk", hidden_disk, FROMEQU
 trusted,?		{ libxl_defbool_set(&DPC->disk->trusted, true); }
 untrusted,?		{ libxl_defbool_set(&DPC->disk->trusted, false); }
 
+grant_usage=1,?		{ libxl_defbool_set(&DPC->disk->grant_usage, true); }
+grant_usage=0,?		{ libxl_defbool_set(&DPC->disk->grant_usage, false); }
+
  /* the target magic parameter, eats the rest of the string */
 
 target=.*	{ STRIP(','); SAVESTRING("target", pdev_path, FROMEQUALS); }