xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
for restricting device emulators (such as QEMU) to a limited set of
hypervisor operations, and being able to audit those operations in the
kernel of the domain in which they run.

This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.

NOTE: There is no requirement for user-space code to bounce data through
      locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
      privcmd has enough information to lock the original buffers
      directly.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

include/xen/interface/hvm/dm_op.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2016, Citrix Systems Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef __XEN_PUBLIC_HVM_DM_OP_H__
+#define __XEN_PUBLIC_HVM_DM_OP_H__
+
+struct xen_dm_op_buf {
+	GUEST_HANDLE(void) h;
+	xen_ulong_t size;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xen_dm_op_buf);
+
+#endif /* __XEN_PUBLIC_HVM_DM_OP_H__ */

include/xen/interface/xen.h

@@ -81,6 +81,7 @@
 #define __HYPERVISOR_tmem_op              38
 #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
 #define __HYPERVISOR_xenpmu_op            40
+#define __HYPERVISOR_dm_op                41
 
 /* Architecture-specific hypercall definitions. */
 #define __HYPERVISOR_arch_0               48