49 lines
1.8 KiB
Diff
49 lines
1.8 KiB
Diff
From cc173deaaa4d9dc6ad9188e0b03f46b7e64f26b2 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 13:36:57 +0100
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Subject: [PATCH 45/57] hw/net/rtl8139: skip automatic zero-init of large 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: 382: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED
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RH-Jira: RHEL-99888
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [19/30] 344c720aef2feb35f84fd4b21f2b1b31e5572286 (stefanha/centos-stream-qemu-kvm)
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The 'rtl8139_transmit_one' method has a 8k byte array used for
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copying data between guest and host. Skip the automatic zero-init
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of this array to eliminate the performance overhead in the I/O
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hot path.
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The 'txbuffer' will be fully initialized when reading PCI DMA
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buffers.
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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: 20250610123709.835102-20-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 3ccc6489dd4925ddd1f3066bd3751389169cd7aa)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/net/rtl8139.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
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index f2fe057535..a2732bf1c1 100644
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--- a/hw/net/rtl8139.c
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+++ b/hw/net/rtl8139.c
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@@ -1818,7 +1818,7 @@ static int rtl8139_transmit_one(RTL8139State *s, int descriptor)
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PCIDevice *d = PCI_DEVICE(s);
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int txsize = s->TxStatus[descriptor] & 0x1fff;
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- uint8_t txbuffer[0x2000];
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+ QEMU_UNINITIALIZED uint8_t txbuffer[0x2000];
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DPRINTF("+++ transmit reading %d bytes from host memory at 0x%08x\n",
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txsize, s->TxAddr[descriptor]);
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--
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2.39.3
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