[PATCH V2] libxl: Add "grant_usage" parameter for virtio disk devices

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

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@xxxxxxxx>
---
In addition to "libxl: arm: Add grant_usage parameter for virtio devices"
https://github.com/xen-project/xen/commit/c14254065ff4826e34f714e1790eab5217368c38

I wonder, whether I had to also include autogenerated changes to:
 - tools/libs/util/libxlu_disk_l.c
 - tools/libs/util/libxlu_disk_l.h

 V2:
  - clarify documentation to match the implementation
  - apply a default value if "grant_usage" is missing in the Xenstore
    in libxl__disk_from_xenstore()
---
 docs/man/xl-disk-configuration.5.pod.in | 24 ++++++++++++++++++++++++
 tools/golang/xenlight/helpers.gen.go    |  6 ++++++
 tools/golang/xenlight/types.gen.go      |  1 +
 tools/include/libxl.h                   |  7 +++++++
 tools/libs/light/libxl_arm.c            |  4 ++--
 tools/libs/light/libxl_disk.c           | 14 ++++++++++++++
 tools/libs/light/libxl_types.idl        |  1 +
 tools/libs/util/libxlu_disk_l.l         |  3 +++
 8 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/docs/man/xl-disk-configuration.5.pod.in 
b/docs/man/xl-disk-configuration.5.pod.in
index bc945cc517..55e78005cf 100644
--- a/docs/man/xl-disk-configuration.5.pod.in
+++ b/docs/man/xl-disk-configuration.5.pod.in
@@ -404,6 +404,30 @@ 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
diff --git a/tools/golang/xenlight/helpers.gen.go 
b/tools/golang/xenlight/helpers.gen.go
index 35e209ff1b..768ab0f566 100644
--- a/tools/golang/xenlight/helpers.gen.go
+++ b/tools/golang/xenlight/helpers.gen.go
@@ -1879,6 +1879,9 @@ 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}
@@ -1927,6 +1930,9 @@ 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
diff --git a/tools/golang/xenlight/types.gen.go 
b/tools/golang/xenlight/types.gen.go
index 7907aa8999..0b712d2aa4 100644
--- a/tools/golang/xenlight/types.gen.go
+++ b/tools/golang/xenlight/types.gen.go
@@ -740,6 +740,7 @@ ColoExport string
 ActiveDisk string
 HiddenDisk string
 Trusted Defbool
+GrantUsage Defbool
 }
 
 type DeviceNic struct {
diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index f1652b1664..2b69e08466 100644
--- a/tools/include/libxl.h
+++ b/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.
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 1539191774..1cb89fa584 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/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)) );
             }
         }
 
diff --git a/tools/libs/light/libxl_disk.c b/tools/libs/light/libxl_disk.c
index ea3623dd6f..ed02b655a3 100644
--- a/tools/libs/light/libxl_disk.c
+++ b/tools/libs/light/libxl_disk.c
@@ -181,6 +181,9 @@ 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) {
@@ -429,6 +432,8 @@ 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");
@@ -623,6 +628,15 @@ 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) {
+            LOG(DEBUG, "Missing xenstore node %s/grant_usage, using default 
value", libxl_path);
+            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,
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 899ad30969..6d76f25528 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/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", [
diff --git a/tools/libs/util/libxlu_disk_l.l b/tools/libs/util/libxlu_disk_l.l
index 6d53c093a3..f37dd443bd 100644
--- a/tools/libs/util/libxlu_disk_l.l
+++ b/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); }
-- 
2.34.1