hw/char/sclpconsole-lm: skip automatic zero-init of large array

The 'process_mdb' method has a 4k byte array used for copying data
between the guest and the chardev backend. Skip the automatic zero-init
of this array to eliminate the performance overhead in the I/O hot
path.

The 'buffer' array will be selectively initialized when data is converted
between EBCDIC and ASCII.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-15-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c
index e9580aacba8c41339cd5b0c8e26ccae72ef134db..3e40d5e43424051af504bf216395dc32b637584d 100644 (file)
--- a/hw/char/sclpconsole-lm.c
+++ b/hw/char/sclpconsole-lm.c
@@ -214,7 +214,7 @@ static int process_mdb(SCLPEvent *event, MDBO *mdbo)
 {
     int rc;
     int len;
-    uint8_t buffer[SIZE_BUFFER];
+    QEMU_UNINITIALIZED uint8_t buffer[SIZE_BUFFER];
 
     len = be16_to_cpu(mdbo->length);
     len -= sizeof(mdbo->length) + sizeof(mdbo->type)