[Qemu-devel] [PATCH QEMU-XEN v8 6/8] xen: Use stable library interfaces when they are available.

[Ian Campbell <ian.campbell@citrix.com>]

In Xen 4.7 we are refactoring parts libxenctrl into a number of
separate libraries which will provide backward and forward API and ABI
compatiblity.

Specifically libxenevtchn, libxengnttab and libxenforeignmemory.

Previous patches have already laid the groundwork for using these by
switching the existing compatibility shims to reflect the intefaces to
these libraries.

So all which remains is to update configure to detect the libraries
and enable their use. Although they are notionally independent we take
an all or nothing approach to the three libraries since they were
added at the same time.

The only non-obvious bit is that we now open a proper xenforeignmemory
handle for xen_fmem instead of reusing the xen_xc handle.

Build tested with 4.0 .. 4.6 (inclusive) and the patches targetting
4.7 which adds these libraries.

This uses CONFIG_XEN_CTRL_INTERFACE_VERSION == 471 to cover the
introduction of these new interfaces.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---

v8: Use CONFIG_XEN_CTRL_INTERFACE_VERSION == 471 for new interfaces.
    Dropped Reviewed-by.

v6: Two minor formatting things.
    Rebase onto "xen: fix usage of xc_domain_create in domain
    builder", required adjusting the configure script changes.

    The rebase wasn't entirely trivial (semantically), so dropped
    Stefano's reviwed by.

v5: Remove ifdef check when undeffing the compat stuff.
    s/now way/no way/

v4: xenforeignmemory_open is now a compat wrapper, so no ifdef.

    Simplify configury by asserting that interface version 470 will
    always have the libraries (lack of them makes it 460).

    Ran checkpatch and fixed everything except:

ERROR: need consistent spacing around '*' (ctx:WxV)
+typedef xc_interface *XenXC;

Which I think is a false +ve.

Simpler configure stuff
---
 configure                   | 55 +++++++++++++++++++++++++++++++++++++++++++++
 include/hw/xen/xen_common.h | 35 +++++++++++++++++++++++++++--
 2 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 44ac9ab..9ead31d 100755
--- a/configure
+++ b/configure
@@ -1938,6 +1938,7 @@ fi
 
 if test "$xen" != "no" ; then
   xen_libs="-lxenstore -lxenctrl -lxenguest"
+  xen_stable_libs="-lxenforeignmemory -lxengnttab -lxenevtchn"
 
   # First we test whether Xen headers and libraries are available.
   # If no, we are done and there is no Xen support.
@@ -1960,6 +1961,57 @@ EOF
   # Xen unstable
   elif
       cat > $TMPC <<EOF &&
+/*
+ * If we have stable libs the we don't want the libxc compat
+ * layers, regardless of what CFLAGS we may have been given.
+ */
+#undef XC_WANT_COMPAT_EVTCHN_API
+#undef XC_WANT_COMPAT_GNTTAB_API
+#undef XC_WANT_COMPAT_MAP_FOREIGN_API
+#include <xenctrl.h>
+#include <xenstore.h>
+#include <xenevtchn.h>
+#include <xengnttab.h>
+#include <xenforeignmemory.h>
+#include <stdint.h>
+#include <xen/hvm/hvm_info_table.h>
+#if !defined(HVM_MAX_VCPUS)
+# error HVM_MAX_VCPUS not defined
+#endif
+int main(void) {
+  xc_interface *xc = NULL;
+  xenforeignmemory_handle *xfmem;
+  xenevtchn_handle *xe;
+  xengnttab_handle *xg;
+  xen_domain_handle_t handle;
+
+  xs_daemon_open();
+
+  xc = xc_interface_open(0, 0, 0);
+  xc_hvm_set_mem_type(0, 0, HVMMEM_ram_ro, 0, 0);
+  xc_domain_add_to_physmap(0, 0, XENMAPSPACE_gmfn, 0, 0);
+  xc_hvm_inject_msi(xc, 0, 0xf0000000, 0x00000000);
+  xc_hvm_create_ioreq_server(xc, 0, HVM_IOREQSRV_BUFIOREQ_ATOMIC, NULL);
+  xc_domain_create(xc, 0, handle, 0, NULL, NULL);
+
+  xfmem = xenforeignmemory_open(0, 0);
+  xenforeignmemory_map(xfmem, 0, 0, 0, 0, 0);
+
+  xe = xenevtchn_open(0, 0);
+  xenevtchn_fd(xe);
+
+  xg = xengnttab_open(0, 0);
+  xengnttab_map_grant_ref(xg, 0, 0, 0);
+
+  return 0;
+}
+EOF
+      compile_prog "" "$xen_libs $xen_stable_libs"
+    then
+    xen_ctrl_version=471
+    xen=yes
+  elif
+      cat > $TMPC <<EOF &&
 #include <xenctrl.h>
 #include <stdint.h>
 int main(void) {
@@ -2153,6 +2205,9 @@ EOF
   fi
 
   if test "$xen" = yes; then
+    if test $xen_ctrl_version -ge 471  ; then
+      libs_softmmu="$xen_stable_libs $libs_softmmu"
+    fi
     libs_softmmu="$xen_libs $libs_softmmu"
   fi
 fi
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 95275b3..19f1577 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -6,6 +6,15 @@
 #include <stddef.h>
 #include <inttypes.h>
 
+/*
+ * If we have new enough libxenctrl then we do not want/need these compat
+ * interfaces, despite what the user supplied cflags might say. They
+ * must be undefined before including xenctrl.h
+ */
+#undef XC_WANT_COMPAT_EVTCHN_API
+#undef XC_WANT_COMPAT_GNTTAB_API
+#undef XC_WANT_COMPAT_MAP_FOREIGN_API
+
 #include <xenctrl.h>
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 420
 #  include <xs.h>
@@ -148,8 +157,8 @@ static inline void xs_close(struct xs_handle *xsh)
 }
 
 
-/* Xen 4.1 */
-#else
+/* Xen 4.1 thru 4.6 */
+#elif CONFIG_XEN_CTRL_INTERFACE_VERSION < 471
 
 typedef xc_interface *XenXC;
 typedef xc_interface *xenforeignmemory_handle;
@@ -184,6 +193,28 @@ static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
 
 /* See below for xenforeignmemory_* APIs */
 
+/* FIXME There is no way to have the xen fd */
+static inline int xc_fd(xc_interface *xen_xc)
+{
+    return -1;
+}
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 471 */
+
+typedef xc_interface *XenXC;
+
+#  define XC_INTERFACE_FMT "%p"
+#  define XC_HANDLER_INITIAL_VALUE    NULL
+
+#include <xenevtchn.h>
+#include <xengnttab.h>
+#include <xenforeignmemory.h>
+
+static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
+                                          unsigned int open_flags)
+{
+    return xc_interface_open(logger, dombuild_logger, open_flags);
+}
+
 /* FIXME There is now way to have the xen fd */
 static inline int xc_fd(xc_interface *xen_xc)
 {
-- 
2.1.4