net/stream: skip automatic zero-init of large array

The 'net_stream_send' method has a 68k byte array used for copying
data between guest and host. Skip the automatic zero-init of this
array to eliminate the performance overhead in the I/O hot path.

The 'buf1' array will be fully initialized when reading data off
the network socket.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-id: 20250610123709.835102-32-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 837b87c4c5)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

net/stream.c

@@ -148,7 +148,7 @@ static gboolean net_stream_send(QIOChannel *ioc,
     NetStreamState *s = data;
     int size;
     int ret;
-    char buf1[NET_BUFSIZE];
+    QEMU_UNINITIALIZED char buf1[NET_BUFSIZE];
     const char *buf;
 
     size = qio_channel_read(s->ioc, buf1, sizeof(buf1), NULL);