From: Daniel P. Berrangé <berrange@redhat.com>
Date: Tue, 10 Jun 2025 12:37:07 +0000 (+0100)
Subject: hw/ufs/lu: skip automatic zero-init of large array
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7708e298180550eac262c1fd742e6e80c711a5d8;p=thirdparty%2Fqemu.git

hw/ufs/lu: skip automatic zero-init of large array

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

The 'outbuf' array will be fully initialized when data is copied
from the guest.

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: 20250610123709.835102-30-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---

diff --git a/hw/ufs/lu.c b/hw/ufs/lu.c
index 57b307ea56..2d8ffd72c5 100644
--- a/hw/ufs/lu.c
+++ b/hw/ufs/lu.c
@@ -194,7 +194,7 @@ static int ufs_emulate_wlun_inquiry(UfsRequest *req, uint8_t *outbuf,
 static UfsReqResult ufs_emulate_scsi_cmd(UfsLu *lu, UfsRequest *req)
 {
     uint8_t lun = lu->lun;
-    uint8_t outbuf[4096];
+    QEMU_UNINITIALIZED uint8_t outbuf[4096];
     uint8_t sense_buf[UFS_SENSE_SIZE];
     uint8_t scsi_status;
     int len = 0;