xen/dmop: Strip __XEN_TOOLS__ header guard from public ABI

__XEN_TOOLS__ is really there to separate the unstable from stable hypercalls.
Exactly as with c/s f40e1c52e4, stable interfaces shouldn't contain this
guard.

That change actually broke the build with:

  include/xendevicemodel.h:52:5: error: unknown type name 'ioservid_t'
       ioservid_t *id);
       ^

as libxendevicemodel.h now uses a type it can't see a typedef for.  However,
nothing noticed because the header.chk logic is also broken (fixed
subsequently).

Strip the guard from the public header, and remove compensation from
devicemodel's private.h.  Fix the dmop design doc to discuss both reasons
behind the the ABI design.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

docs/designs/dmop.pandoc

@@ -4,9 +4,15 @@ DMOP
 Introduction
 ------------
 
-The aim of DMOP is to prevent a compromised device model from compromising
-domains other than the one it is providing emulation for (which is therefore
-likely already compromised).
+The DMOP hypercall has a new ABI design to solve problems in the Xen
+ecosystem.  First, the ABI is fully stable, to reduce the coupling between
+device models and the version of Xen.  Specifically, device model software
+using DMOP (be it user, stub domain or kernel software) need not be recompiled
+to match the version of the running hypervisor.
+
+Secondly, for device models in userspace, the ABI is designed specifically to
+allow a kernel to audit the memory ranges used, without having to know the
+internal structure of sub-ops.
 
 The problem occurs when you a device model issues an hypercall that
 includes references to user memory other than the operation structure

tools/libs/devicemodel/private.h

@@ -1,8 +1,6 @@
 #ifndef XENDEVICEMODEL_PRIVATE_H
 #define XENDEVICEMODEL_PRIVATE_H
 
-#define __XEN_TOOLS__ 1
-
 #include <xentoollog.h>
 #include <xendevicemodel.h>
 #include <xencall.h>

xen/include/public/hvm/dm_op.h

@@ -25,9 +25,6 @@
 #define __XEN_PUBLIC_HVM_DM_OP_H__
 
 #include "../xen.h"
-
-#if defined(__XEN__) || defined(__XEN_TOOLS__)
-
 #include "../event_channel.h"
 
 #ifndef uint64_aligned_t
@@ -491,8 +488,6 @@ struct xen_dm_op {
     } u;
 };
 
-#endif /* __XEN__ || __XEN_TOOLS__ */
-
 struct xen_dm_op_buf {
     XEN_GUEST_HANDLE(void) h;
     xen_ulong_t size;