migration: Add direct-io parameter

Add the direct-io migration parameter that tells the migration code to
use O_DIRECT when opening the migration stream file whenever possible.

This is currently only used with the mapped-ram migration that has a
clear window guaranteed to perform aligned writes.

Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

1 files changed, 9 insertions, 0 deletions

diff --git a/util/osdep.c b/util/osdep.c
index 5bbfdfac7a..770369831b 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -282,6 +282,15 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive)
 }
 #endif
 
+bool qemu_has_direct_io(void)
+{
+#ifdef O_DIRECT
+    return true;
+#else
+    return false;
+#endif
+}
+
 static int qemu_open_cloexec(const char *name, int flags, mode_t mode)
 {
     int ret;