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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <54B57C51.7090002@wiesinger.com> (Gerhard Wiesinger's message of
	"Tue, 13 Jan 2015 21:13:05 +0100")
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Date: Wed, 14 Jan 2015 18:47:52 +0100
Message-ID: <87h9vtmeyf.fsf@elfo.elfo>
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Subject: Re: [Qemu-devel] Fedora FC21 - Bug: 100% CPU and hangs in
	gettimeofday(&tp, NULL); forever
Reply-To: quintela@redhat.com
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To: Gerhard Wiesinger <lists@wiesinger.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org

Gerhard Wiesinger <lists@wiesinger.com> wrote:
> On 12.01.2015 12:41, Gerhard Wiesinger wrote:
>> On 08.01.2015 23:28, Gerhard Wiesinger wrote:
>>>
>>> I'll keep you up to date in the next days whether it happens again
>>> or not.
>>
>> With qemu-kvm 2.2.0 release from the above repository the 100% usage
>> didn't happen so far (although I had to reboot after kernel update).
>
> It happens also with qemu-kvm 2.2.0 on another VM where also
> PostgreSQL is running:
> (gdb) bt
> #0  0x00007fff9a1feff4 in gettimeofday ()
> #1  0x00000000006d425e in GetCurrentTimestamp () at timestamp.c:1274
>
> What we know:
> OK : F20: 3.17.6-200.fc20.x86_64 on guest/host,
> qemu-kvm-1.6.2-10.fc20.x86_64 on host
> NOK: F21: 3.17.7-300.fc21.x86_64 on guest/host,
> qemu-kvm-2.1.2-7.fc21.x86_64 on host
> NOK: F21: 3.17.8-300.fc21.x86_64 on guest/host,
> qemu-kvm-2.2.0-1.fc21.x86_64 on host
>
> No one less can reproduce or has similar problems?

I have similar problems, F21 guest on F21 host.
https://bugzilla.redhat.com/show_bug.cgi?id=1174664

For me, it is firefox that from time to time loops on vclock_gettime().
At that point the DSO have got corrupted (kvmclock msr's), and as you
say, only solution is reboot.  Could you look at the bug, and see if the
areas pointed by the MSR also got corrupted?  I tried using kernel-debug
with debugging for memory allocation (marcelo request).  I see pattens
like 0x5a5a5a5a, so clearly there is some corruption, but haven't been
able to find _what_ is making that happen.

> Any further ideas?

Nope :-(

> BTW: I'm running ntp in the following manner: internet <=> ntp server
> in VM <=> ntp client on KVM host (firewall runs in KVM)

I am uisng ntp on the host against Internet, but the guest don't use ntp
(I do a ntpdate if I see that the guest has drifted too much, and it is
a rare event.  Right now I don't rememeber having fixed it lately).

Later, Juan.