hw/net/tulip: skip automatic zero-init of large array

The 'tulip_setup_frame' method has a 4k byte array used for copynig
DMA data from the device. Skip the automatic zero-init of this array
to eliminate the performance overhead in the I/O hot path.

The 'buf' array will be fully initialized when reading data from the
device.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-21-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/hw/net/tulip.c b/hw/net/tulip.c
index 63fe5134586335157ce2fd6e0a5dfd5b1e373f3d..319af906c8d2acbdd39fa77f7042f3f74fe76fda 100644 (file)
--- a/hw/net/tulip.c
+++ b/hw/net/tulip.c
@@ -629,7 +629,7 @@ static void tulip_setup_filter_addr(TULIPState *s, uint8_t *buf, int n)
 static void tulip_setup_frame(TULIPState *s,
         struct tulip_descriptor *desc)
 {
-    uint8_t buf[4096];
+    QEMU_UNINITIALIZED uint8_t buf[4096];
     int len = (desc->control >> TDES1_BUF1_SIZE_SHIFT) & TDES1_BUF1_SIZE_MASK;
     int i;