9p: darwin: meson: Allow VirtFS on Darwin

To allow VirtFS on darwin, we need to check that pthread_fchdir_np is
available, which has only been available since macOS 10.12.

Additionally, virtfs_proxy_helper is disabled on Darwin. This patch
series does not currently provide an implementation of the proxy-helper,
but this functionality could be implemented later on.

Signed-off-by: Keno Fischer <keno@juliacomputing.com>
[Michael Roitzsch: - Rebase for NixOS]
Signed-off-by: Michael Roitzsch <reactorcontrol@icloud.com>
[Will Cohen: - Rebase to master]
Signed-off-by: Will Cohen <wwcohen@gmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
[Will Cohen: - Add check for pthread_fchdir_np to virtfs
             - Add comments to patch commit
             - Note that virtfs_proxy_helper does not work
               on macOS
             - Fully adjust meson virtfs error note to specify
               macOS
             - Rebase to master]
Signed-off-by: Will Cohen <wwcohen@gmail.com>
Message-Id: <20220227223522.91937-12-wwcohen@gmail.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Acked-by: Christian Schoenebeck <qemu_oss@crudebyte.com>

fsdev/meson.build

@@ -7,6 +7,7 @@ fsdev_ss.add(when: ['CONFIG_FSDEV_9P'], if_true: files(
   'qemu-fsdev.c',
 ), if_false: files('qemu-fsdev-dummy.c'))
 softmmu_ss.add_all(when: 'CONFIG_LINUX', if_true: fsdev_ss)
+softmmu_ss.add_all(when: 'CONFIG_DARWIN', if_true: fsdev_ss)
 
 if have_virtfs_proxy_helper
   executable('virtfs-proxy-helper',

meson.build

@@ -1462,14 +1462,16 @@ dbus_display = get_option('dbus_display') \
   .allowed()
 
 have_virtfs = get_option('virtfs') \
-    .require(targetos == 'linux',
-             error_message: 'virtio-9p (virtfs) requires Linux') \
-    .require(libattr.found() and libcap_ng.found(),
-             error_message: 'virtio-9p (virtfs) requires libcap-ng-devel and libattr-devel') \
+    .require(targetos == 'linux' or targetos == 'darwin',
+             error_message: 'virtio-9p (virtfs) requires Linux or macOS') \
+    .require(targetos == 'linux' or cc.has_function('pthread_fchdir_np'),
+             error_message: 'virtio-9p (virtfs) on macOS requires the presence of pthread_fchdir_np') \
+    .require(targetos == 'darwin' or (libattr.found() and libcap_ng.found()),
+             error_message: 'virtio-9p (virtfs) on Linux requires libcap-ng-devel and libattr-devel') \
     .disable_auto_if(not have_tools and not have_system) \
     .allowed()
 
-have_virtfs_proxy_helper = have_virtfs and have_tools
+have_virtfs_proxy_helper = targetos != 'darwin' and have_virtfs and have_tools
 
 foreach k : get_option('trace_backends')
   config_host_data.set('CONFIG_TRACE_' + k.to_upper(), true)