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[PULL 27/31] hw/scsi/lsi53c895a: skip automatic zero-init of large array


From: Stefan Hajnoczi
Subject: [PULL 27/31] hw/scsi/lsi53c895a: skip automatic zero-init of large array
Date: Wed, 11 Jun 2025 14:25:29 -0400

From: Daniel P. Berrangé <berrange@redhat.com>

The 'lsi_memcpy' method has a 4k byte array used for copying data
to/from the device. 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>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-id: 20250610123709.835102-28-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/scsi/lsi53c895a.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index f4f2ef321e..9ea4aa0a85 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -1112,7 +1112,7 @@ bad:
 static void lsi_memcpy(LSIState *s, uint32_t dest, uint32_t src, int count)
 {
     int n;
-    uint8_t buf[LSI_BUF_SIZE];
+    QEMU_UNINITIALIZED uint8_t buf[LSI_BUF_SIZE];
 
     trace_lsi_memcpy(dest, src, count);
     while (count) {
-- 
2.49.0




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