qemu-kvm/SOURCES/kvm-hw-audio-ac97-skip-automatic-zero-init-of-large-arra.patch

50 lines
1.8 KiB
Diff

From 2553d2d26a9d0f46386bf8c37d184567e5cede6c 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 13:36:45 +0100
Subject: [PATCH] hw/audio/ac97: skip automatic zero-init of large arrays
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
The 'read_audio' & 'write_audio' methods have a 4k byte array used
for copying data between the audio backend and device. Skip the
automatic zero-init of these arrays to eliminate the performance
overhead in the I/O hot path.
The 'tmpbuf' array will be fully initialized when reading data from
the audio backend and/or device memory.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-8-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/audio/ac97.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/audio/ac97.c b/hw/audio/ac97.c
index 669a0463cc..eb7a847080 100644
--- a/hw/audio/ac97.c
+++ b/hw/audio/ac97.c
@@ -886,7 +886,7 @@ static void nabm_writel(void *opaque, uint32_t addr, uint32_t val)
static int write_audio(AC97LinkState *s, AC97BusMasterRegs *r,
int max, int *stop)
{
- uint8_t tmpbuf[4096];
+ QEMU_UNINITIALIZED uint8_t tmpbuf[4096];
uint32_t addr = r->bd.addr;
uint32_t temp = r->picb << 1;
uint32_t written = 0;
@@ -959,7 +959,7 @@ static void write_bup(AC97LinkState *s, int elapsed)
static int read_audio(AC97LinkState *s, AC97BusMasterRegs *r,
int max, int *stop)
{
- uint8_t tmpbuf[4096];
+ QEMU_UNINITIALIZED uint8_t tmpbuf[4096];
uint32_t addr = r->bd.addr;
uint32_t temp = r->picb << 1;
uint32_t nread = 0;
--
2.47.3