50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
From 3179e7e183295b91e314c32db8697d8cf0947367 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
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Date: Tue, 10 Jun 2025 13:37:05 +0100
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Subject: [PATCH 27/31] hw/scsi/lsi53c895a: skip automatic zero-init of large
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array
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 461: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED
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RH-Jira: RHEL-99887
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [26/30] 92ec0b18f26956767d2f3d0284d712696d60852e
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The 'lsi_memcpy' method has a 4k byte array used for copying data
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to/from the device. Skip the automatic zero-init of this array to
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eliminate the performance overhead in the I/O hot path.
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The 'buf' array will be fully initialized when data is copied.
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Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
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Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
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Message-id: 20250610123709.835102-28-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 55243edf42ee87bce9f36ca251f3ab9cda1563e4)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/scsi/lsi53c895a.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
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index f1935e5328..f165705f8a 100644
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--- a/hw/scsi/lsi53c895a.c
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+++ b/hw/scsi/lsi53c895a.c
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@@ -1112,7 +1112,7 @@ bad:
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static void lsi_memcpy(LSIState *s, uint32_t dest, uint32_t src, int count)
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{
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int n;
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- uint8_t buf[LSI_BUF_SIZE];
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+ QEMU_UNINITIALIZED uint8_t buf[LSI_BUF_SIZE];
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trace_lsi_memcpy(dest, src, count);
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while (count) {
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--
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2.39.3
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