57 lines
2.1 KiB
Diff
57 lines
2.1 KiB
Diff
From c7b6fe3f924396dd49bdf13485696a536aa34fb0 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 13:36:55 +0100
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Subject: [PATCH 18/31] hw/hyperv/syndbg: 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: [17/30] 4202f998aff3fd784508ab6e52658cecd197924b
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The 'handle_recv_msg' method has a 4k byte array used for copying
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data between the network socket and guest memory. Skip the automatic
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zero-init of this array to eliminate the performance overhead in the
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I/O hot path.
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The 'data_buf' array will be fully initialized when data is read
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off the network socket.
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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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Message-id: 20250610123709.835102-18-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 5a1f614d0cd0bcc8e84e0b7ab6af63d56bd348a2)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Conflicts:
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hw/hyperv/syndbg.c
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Context conflict due to missing commit 3efb9d226221
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("hw/hyperv/syndbg: common compilation unit") downstream. There is no
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need to backport the commit because it's not a bug fix.
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---
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hw/hyperv/syndbg.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/hw/hyperv/syndbg.c b/hw/hyperv/syndbg.c
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index 065e12fb1e..c7c43c8009 100644
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--- a/hw/hyperv/syndbg.c
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+++ b/hw/hyperv/syndbg.c
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@@ -188,7 +188,7 @@ static uint16_t handle_recv_msg(HvSynDbg *syndbg, uint64_t outgpa,
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uint64_t timeout, uint32_t *retrieved_count)
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{
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uint16_t ret;
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- uint8_t data_buf[TARGET_PAGE_SIZE - UDP_PKT_HEADER_SIZE];
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+ QEMU_UNINITIALIZED uint8_t data_buf[TARGET_PAGE_SIZE - UDP_PKT_HEADER_SIZE];
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hwaddr out_len;
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void *out_data;
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ssize_t recv_byte_count;
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--
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2.39.3
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