From: Daniel P. Berrangé <berrange@redhat.com>
Date: Tue, 10 Jun 2025 12:36:48 +0000 (+0100)
Subject: hw/audio/gus: skip automatic zero-init of large array
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2e438da4929018c62609381e1156aac0b2fe3de3;p=thirdparty%2Fqemu.git

hw/audio/gus: skip automatic zero-init of large array

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

The 'tmpbuf' array will be fully initialized when reading data
from device memory.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-11-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---

diff --git a/hw/audio/gus.c b/hw/audio/gus.c
index 87e8634893..c36df0240f 100644
--- a/hw/audio/gus.c
+++ b/hw/audio/gus.c
@@ -183,7 +183,7 @@ static int GUS_read_DMA (void *opaque, int nchan, int dma_pos, int dma_len)
 {
     GUSState *s = opaque;
     IsaDmaClass *k = ISADMA_GET_CLASS(s->isa_dma);
-    char tmpbuf[4096];
+    QEMU_UNINITIALIZED char tmpbuf[4096];
     int pos = dma_pos, mode, left = dma_len - dma_pos;
 
     ldebug ("read DMA %#x %d\n", dma_pos, dma_len);