From f8394b69cee118293a1983ebc99492f113d57704 Mon Sep 17 00:00:00 2001
From: Igor Mammedov <imammedo@redhat.com>
Date: Wed, 6 Dec 2017 13:47:58 +0100
Subject: [PATCH 20/21] pc: fix crash on attempted cpu unplug

RH-Author: Igor Mammedov <imammedo@redhat.com>
Message-id: <1512568078-280557-1-git-send-email-imammedo@redhat.com>
Patchwork-id: 78212
O-Subject: [RHEL7.5 qemu-kvm-rhev PATCH] pc: fix crash on attempted cpu unplug
Bugzilla: 1506856
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Marcel Apfelbaum <marcel@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

when qemu is started with '-no-acpi' CLI option, an attempt
to unplug a CPU using device_del results in null pointer
dereference at:

  #0 object_get_class
  #1 pc_machine_device_unplug_request_cb
  #2 qmp_marshal_device_del

which is caused by pcms->acpi_dev == NULL due to ACPI support
being disabled.

Considering that ACPI support is necessary for unplug to work,
check that it's enabled and fail unplug request gracefully
if no acpi device were found.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 75ba2ddb188fa07c3442446766782036e3085cba)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/i386/pc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index f37d60a..db57b51 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1879,6 +1879,11 @@ static void pc_cpu_unplug_request_cb(HotplugHandler *hotplug_dev,
     X86CPU *cpu = X86_CPU(dev);
     PCMachineState *pcms = PC_MACHINE(hotplug_dev);
 
+    if (!pcms->acpi_dev) {
+        error_setg(&local_err, "CPU hot unplug not supported without ACPI");
+        goto out;
+    }
+
     pc_find_cpu_slot(MACHINE(pcms), cpu->apic_id, &idx);
     assert(idx != -1);
     if (idx == 0) {
-- 
1.8.3.1