hw/audio/ac97: skip automatic zero-init of large arrays

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>

diff --git a/hw/audio/ac97.c b/hw/audio/ac97.c
index 669a0463cc130803b64ff4cff518112c7ab2bedf..eb7a847080da99a3ef73c39ad3628e70e97b22b8 100644 (file)
--- 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;