hw/dma/xlnx_csu_dma: skip automatic zero-init of large array

The 'xlnx_csu_dma_src_notify' method has a 4k byte array used for
copying DMA data. 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 data is copied.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-16-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/hw/dma/xlnx_csu_dma.c b/hw/dma/xlnx_csu_dma.c
index 3db3904d835e1cfd14a295b4621c013752eed2d6..d8c7da1a501c823e87f67d6d4d0c30388fd7d7dd 100644 (file)
--- a/hw/dma/xlnx_csu_dma.c
+++ b/hw/dma/xlnx_csu_dma.c
@@ -287,7 +287,7 @@ static uint32_t xlnx_csu_dma_advance(XlnxCSUDMA *s, uint32_t len)
 static void xlnx_csu_dma_src_notify(void *opaque)
 {
     XlnxCSUDMA *s = XLNX_CSU_DMA(opaque);
-    unsigned char buf[4 * 1024];
+    QEMU_UNINITIALIZED unsigned char buf[4 * 1024];
     size_t rlen = 0;
 
     ptimer_transaction_begin(s->src_timer);