Add cache=unsafe parameter to -drive

Usually the guest can tell the host to flush data to disk. In some cases we
don't want to flush though, but try to keep everything in cache.

So let's add a new cache value to -drive that allows us to set the cache
policy to most aggressive, disabling flushes. We call this mode "unsafe",
as guest data is not guaranteed to survive host crashes anymore.

This patch also adds a noop function for aio, so we can do nothing in AIO
fashion.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index 328395e3d..bc15dd74a 100644
--- a/vl.c
+++ b/vl.c
@@ -913,6 +913,9 @@ DriveInfo *drive_init(QemuOpts *opts, void *opaque,
             bdrv_flags |= BDRV_O_NOCACHE;
         } else if (!strcmp(buf, "writeback")) {
             bdrv_flags |= BDRV_O_CACHE_WB;
+        } else if (!strcmp(buf, "unsafe")) {
+            bdrv_flags |= BDRV_O_CACHE_WB;
+            bdrv_flags |= BDRV_O_NO_FLUSH;
         } else if (!strcmp(buf, "writethrough")) {
             /* this is the default */
         } else {