hw/net/rtl8139: skip automatic zero-init of large array

The 'rtl8139_transmit_one' method has a 8k 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 'txbuffer' will be fully initialized when reading PCI DMA
buffers.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-20-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index 15b8f7501ae6febd2c9d3df4be03846c4332a630..654a087d80ad04a21eccf079bf213aa409a4377d 100644 (file)
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -1816,7 +1816,7 @@ static int rtl8139_transmit_one(RTL8139State *s, int descriptor)
 
     PCIDevice *d = PCI_DEVICE(s);
     int txsize = s->TxStatus[descriptor] & 0x1fff;
-    uint8_t txbuffer[0x2000];
+    QEMU_UNINITIALIZED uint8_t txbuffer[0x2000];
 
     DPRINTF("+++ transmit reading %d bytes from host memory at 0x%08x\n",
         txsize, s->TxAddr[descriptor]);