Blame SOURCES/kvm-skip-system-call-when-msi-route-is-unchanged.patch

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From 00a2c1d4f4dff271a314f0e9eb3b4c873b1a06c1 Mon Sep 17 00:00:00 2001
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From: Michael S. Tsirkin <mst@redhat.com>
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Date: Mon, 19 May 2014 09:57:40 +0200
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Subject: [PATCH 2/2] kvm: skip system call when msi route is unchanged
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RH-Author: Michael S. Tsirkin <mst@redhat.com>
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Message-id: <1400493448-29146-3-git-send-email-mst@redhat.com>
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Patchwork-id: 58949
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O-Subject: [PATCH qemu-kvm RHEL7.1 2/2] kvm: skip system call when msi route is unchanged
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Bugzilla: 1110693
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Marcel Apfelbaum <marcel.a@redhat.com>
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RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
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Some guests do a large number of mask/unmask
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calls which currently trigger expensive route update
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system calls.
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Detect that route in unchanged and skip the system call.
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Reported-by: "Zhanghaoyu (A)" <haoyu.zhang@huawei.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Gleb Natapov <gleb@redhat.com>
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(cherry picked from commit 40509f7f52672fe41c2cce895e187352fc09f53a)
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---
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 kvm-all.c | 4 ++++
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 1 file changed, 4 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 kvm-all.c |    4 ++++
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 1 files changed, 4 insertions(+), 0 deletions(-)
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diff --git a/kvm-all.c b/kvm-all.c
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index 592301a..f7f621b 100644
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--- a/kvm-all.c
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+++ b/kvm-all.c
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@@ -1008,6 +1008,10 @@ static int kvm_update_routing_entry(KVMState *s,
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             continue;
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         }
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+        if(!memcmp(entry, new_entry, sizeof *entry)) {
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+            return 0;
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+        }
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+
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         *entry = *new_entry;
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         kvm_irqchip_commit_routes(s);
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-- 
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1.7.1
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