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Date: Tue, 15 Jul 2014 22:43:39 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH uq/master] kvmclock: Ensure proper env->tsc
 value for kvmclock_current_nsec calculation
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To: Marcelo Tosatti <mtosatti@redhat.com>, Andrey Korolyov <andrey@xdel.ru>
Cc: =?UTF-8?B?TWFyY2luIEdpYnXFgmE=?= <m.gibula@beyond.pl>, Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org

Il 15/07/2014 22:31, Marcelo Tosatti ha scritto:
> This patch (or some form of updating env->tsc, see changelog) 
> is necessary.

Yes, I was going to revert Alex's too.

> I was just about to reproduce it.
> 
> Andrey, can you please provide the qemu command line ?
> 
> Can you attempt to start VM via command line and migrate
> via QEMU monitor, then gdb -p to get a backtrace for all 
> threads ?

Andrey provided backtraces for this issue here:

http://article.gmane.org/gmane.comp.emulators.qemu/286679

The first backtrace attached is bt-noreset.txt, the second is bt-reset.txt
but they are identical.  The backtraces lack symbols for QEMU, but it looks 
like the VMs are running because the CPU threads all look like this:

Thread 4 (Thread 0x7f0054ff9700 (LWP 2915)):
#0  0x00007f00a04dbc37 in ioctl () at ../sysdeps/unix/syscall-template.S:82
#1  0x00007f00a59ea0a9 in ?? ()
#2  0x00007f00a59ea1e5 in ?? ()
#3  0x00007f00a59d59bc in ?? ()
#4  0x00007f00a07b5e9a in start_thread (arg=0x7f0054ff9700) at pthread_create.c:308
#5  0x00007f00a04e33dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()

where the ioctl is likely KVM_RUN.

Paolo