qemu-kvm/SOURCES/kvm-hw-audio-gus-skip-automatic-zero-init-of-large-array.patch

41 lines
1.4 KiB
Diff

From 2e438da4929018c62609381e1156aac0b2fe3de3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
Date: Tue, 10 Jun 2025 13:36:48 +0100
Subject: [PATCH] hw/audio/gus: skip automatic zero-init of large array
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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>
---
hw/audio/gus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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);
--
2.47.3