osdep: Change default value of qemu_hw_version() to "2.5+"

There are two issues with qemu_hw_version() today:

1) If a machine has hw_version set, the value returned by it is
   not very useful, because it is not the actual QEMU version.
2) If a machine does't set hw_version, the return value of
   qemu_hw_version() is broken, because it will change when
   upgrading QEMU.

For those reasons, using qemu_hw_version() is strongly
discouraged, and should be used only in code that used
QEMU_VERSION in the past and needs to keep compatibility.

To fix (2), instead of making every machine broken by default
unless they set hw_version, make qemu_hw_version() simply return
"2.5+" if qemu_set_hw_version() is not called.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 861d84b..84e84ac 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -256,6 +256,10 @@ static inline void qemu_timersub(const struct timeval *val1,
 
 void qemu_set_cloexec(int fd);
 
+/* QEMU "hardware version" setting. Used to replace code that exposed
+ * QEMU_VERSION to guests in the past and need to keep compatibilty.
+ * Do not use qemu_hw_version() in new code.
+ */
 void qemu_set_hw_version(const char *);
 const char *qemu_hw_version(void);