configure: add libdaxctl support

Add a pair of configure options --{enable,disable}-libdaxctl to control
whether QEMU is compiled with libdaxctl [1]. Libdaxctl is a utility
library for managing the device dax subsystem.

QEMU uses mmap(2) to maps vNVDIMM backends and aligns the mapping
address to the page size (getpagesize(2)) by default. However, some
types of backends may require an alignment different than the page
size. The 'align' option is provided to memory-backend-file to allow
users to specify the proper alignment.

For device dax (e.g., /dev/dax0.0), the 'align' option needs to match
the alignment requirement of the device dax, which can be fetched
through the APIs of libdaxctl version 57 or up.

[1] Libdaxctl is a part of ndctl project.
The project's repository is: https://github.com/pmem/ndctl

For more information about libdaxctl APIs, you can refer to the
comments in source code of: pmem/ndctl/daxctl/lib/libdaxctl.c.
Reviewed-by: NJoao Martins <joao.m.martins@oracle.com>
Signed-off-by: NJingqi Liu <jingqi.liu@intel.com>
Message-Id: <20200429085011.63752-4-jingqi.liu@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

configure

@@ -517,6 +517,7 @@ plugins="no"
 fuzzing="no"
 rng_none="no"
 secret_keyring=""
+libdaxctl=""
 
 supported_cpu="no"
 supported_os="no"
@@ -1621,6 +1622,10 @@ for opt do
   ;;
   --disable-keyring) secret_keyring="no"
   ;;
+  --enable-libdaxctl) libdaxctl=yes
+  ;;
+  --disable-libdaxctl) libdaxctl=no
+  ;;
   *)
       echo "ERROR: unknown option $opt"
       echo "Try '$0 --help' for more information"
@@ -1920,6 +1925,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   libpmem         libpmem support
   xkbcommon       xkbcommon support
   rng-none        dummy RNG, avoid using /dev/(u)random and getrandom()
+  libdaxctl       libdaxctl support
 
 NOTE: The object files are built at the place where configure is launched
 EOF
@@ -6292,6 +6298,24 @@ if test "$libpmem" != "no"; then
 	fi
 fi
 
+##########################################
+# check for libdaxctl
+
+if test "$libdaxctl" != "no"; then
+	if $pkg_config --atleast-version=57 "libdaxctl"; then
+		libdaxctl="yes"
+		libdaxctl_libs=$($pkg_config --libs libdaxctl)
+		libdaxctl_cflags=$($pkg_config --cflags libdaxctl)
+		libs_softmmu="$libs_softmmu $libdaxctl_libs"
+		QEMU_CFLAGS="$QEMU_CFLAGS $libdaxctl_cflags"
+	else
+		if test "$libdaxctl" = "yes" ; then
+			feature_not_found "libdaxctl" "Install libdaxctl"
+		fi
+		libdaxctl="no"
+	fi
+fi
+
 ##########################################
 # check for slirp
 
@@ -6898,6 +6922,7 @@ echo "parallels support $parallels"
 echo "sheepdog support  $sheepdog"
 echo "capstone          $capstone"
 echo "libpmem support   $libpmem"
+echo "libdaxctl support $libdaxctl"
 echo "libudev           $libudev"
 echo "default devices   $default_devices"
 echo "plugin support    $plugins"
@@ -7731,6 +7756,10 @@ if test "$libpmem" = "yes" ; then
   echo "CONFIG_LIBPMEM=y" >> $config_host_mak
 fi
 
+if test "$libdaxctl" = "yes" ; then
+  echo "CONFIG_LIBDAXCTL=y" >> $config_host_mak
+fi
+
 if test "$bochs" = "yes" ; then
   echo "CONFIG_BOCHS=y" >> $config_host_mak
 fi