[ kvm-Bugs-2703537 ] CPU hotplug causes segfault

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Bugs item #2703537, was opened at 2009-03-22 18:07
Message generated for change (Comment added) made by glebn
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2703537&group_id=180599

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Category: None
Group: None
Status: Open
Resolution: None
Priority: 7
Private: No
Submitted By: Technologov (technologov)
Assigned to: Nobody/Anonymous (nobody)
Summary: CPU hotplug causes segfault

Initial Comment:

Host: kvm-84 on Intel or AMD. (RHEL 5/x64)

When I use empty VM and add CPU hotplug several times I get a segfault.

Empty VM is started with PXE networking.
# qemu-kvm -boot n

Now I connect to Qemu monitor and use:
(qemu) cpu_set 1 online
(qemu) cpu_set 2 online
(qemu) cpu_set 3 online
(qemu) cpu_set 4 online
(qemu) cpu_set 5 online

When I add several CPUs like this - Qemu/KVM userspace will crash.

Very easy to reproduce.

GDB:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x43c2b940 (LWP 3667)]
0x0000000000459167 in cpu_get_apic_tpr (env=0x1cef87b0)
    at /root/Linstall/kvm-84rc1/qemu/hw/apic.c:316
316     {
(gdb) c
Continuing.
[Thread 0x4322a940 (LWP 3666) exited]
[Thread 0x43c2b940 (LWP 3667) exited]
[Thread 0x41e28940 (LWP 3660) exited]
[Thread 0x42829940 (LWP 3661) exited]

Program terminated with signal SIGSEGV, Segmentation fault.
The program no longer exists.

Dmesg:
There are no interesting messages in dmesg.

-Alexey, 22.3.2009.

----------------------------------------------------------------------

Comment By: Gleb Natapov (glebn)
Date: 2009-03-23 11:25

Message:
It is a known problem (at least by me). There is a race when APIC is
accessed before it is created.

----------------------------------------------------------------------

Comment By: Technologov (technologov)
Date: 2009-03-23 11:16

Message:
Full GDB output attached.

-Alexey, 23.3.2009.
File Added: gdb_of_cpu_hotplug_crash.txt

----------------------------------------------------------------------

Comment By: Glauber de Oliveira Costa (glommer)
Date: 2009-03-22 18:34

Message:
Can you get a backtrace for all threads in qemu in the moment of the
crash?

thanks

----------------------------------------------------------------------

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https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2703537&group_id=180599
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