From b6904ecdbd09b38339963465dd9bd81c25acf5cc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Tue, 10 Jun 2025 13:37:07 +0100 Subject: [PATCH 37/43] hw/ufs/lu: skip automatic zero-init of large array MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Stefan Hajnoczi RH-MergeRequest: 381: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED RH-Jira: RHEL-95479 RH-Acked-by: Miroslav Rezanina RH-Commit: [29/31] 9b4da8039e1856614cd65981c2ec0a4b59c4e379 (stefanha/centos-stream-qemu-kvm) 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 Reviewed-by: Stefan Hajnoczi Reviewed-by: Klaus Jensen Reviewed-by: Harsh Prateek Bora Message-id: 20250610123709.835102-30-berrange@redhat.com Signed-off-by: Stefan Hajnoczi (cherry picked from commit 7708e298180550eac262c1fd742e6e80c711a5d8) Signed-off-by: Stefan Hajnoczi --- hw/ufs/lu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/ufs/lu.c b/hw/ufs/lu.c index 1c3794b2d4..63e482bf83 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; -- 2.39.3