linux-kernel - Re: linux-3.2.1 + KVM: TSC unstable on Core i5-2400S / H67

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Date:	Thu, 26 Jan 2012 14:48:05 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Johannes Stezenbach <js@...21.net>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: linux-3.2.1 + KVM: TSC unstable on Core i5-2400S / H67

On Thu, Jan 26, 2012 at 04:35:13PM +0100, Johannes Stezenbach wrote:
> On Thu, Jan 26, 2012 at 03:43:27PM +0100, Jan Kiszka wrote:
> > On 2012-01-26 10:46, Johannes Stezenbach wrote:
> > > [16353.270435] Restarting tasks ... 
> > > [16353.270612] BUG: spinlock bad magic on CPU#2, dhclient3/2590
> > > [16353.274702]  lock: ffff880127b9ce08, .magic: 00000000, .owner: dhclient3/2590, .owner_cpu: 2
> > > [16353.276594] Pid: 2590, comm: dhclient3 Not tainted 3.2.1 #2
> > > [16353.278294] done.
> > > [16353.278314] video LNXVIDEO:00: Restoring backlight state
> > > [16353.281627] Call Trace:
> > > [16353.281633]  [<ffffffff81552515>] spin_dump+0x8a/0x8f
> > > [16353.281636]  [<ffffffff81552540>] spin_bug+0x26/0x28
> > > [16353.281639]  [<ffffffff81285af8>] do_raw_spin_unlock+0x1e/0x83
> > > [16353.281643]  [<ffffffff8155912e>] _raw_spin_unlock_irq+0x28/0x5b
> > > [16353.281647]  [<ffffffff8105e427>] get_signal_to_deliver+0x546/0x57c
> > > [16353.281651]  [<ffffffff81001572>] do_signal+0x3e/0x62f
> > > [16353.281654]  [<ffffffff815595b8>] ? retint_restore_args+0x13/0x13
> > > [16353.281657]  [<ffffffff81280079>] ? copy_user_generic_string+0x19/0x40
> > > [16353.281661]  [<ffffffff81142e8c>] ? poll_select_copy_remaining+0xc5/0xe9
> > > [16353.281664]  [<ffffffff81001ba8>] do_notify_resume+0x2c/0x53
> > > [16353.281666]  [<ffffffff8128137e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> > > [16353.281669]  [<ffffffff8155a1d6>] int_signal+0x12/0x17
> > > [16353.472289] tsc = fffffd60248a9f39 last_guest_tsc = 229a823d4b88
> > > [    0.006666] Marking TSC unstable due to KVM discovered backwards TSC
> > > [16362.155512] Switching to clocksource hpet
> > > [16363.617844] atl1c 0000:06:00.0: atl1c: eth0 NIC Link is Up<1000 Mbps Full Duplex>
> > > [16363.618145] br0: port 1(eth0) entering forwarding state
> > > [16363.618153] br0: port 1(eth0) entering forwarding state
> > 
> > Are you suspending your host while a VM is running? There is mosto
> 
> Yes, that's what I'm doing.
> 
> > probably a long-pending bug in the KVM TSC check logic that declares
> > that clocksource unstable after resume. I'm seeing this here for ages
> > and complained about it from the beginning (but I never debugged it :-/).
> 
> Hm, OK.  I hope someone has an idea how to fix it.  I'm ready to test patches.
> 
> > Of course, this doesn't explain your corrupted spin lock. That might be
> > a different issue.
> 
> Yes, most probably it is something different since I haven't seen this
> before.  However, I didn't use 3.2.1 long.  Now I updated
> to 3.2.2 and enabled a few more debug options.  We'll see if it
> triggers again.

There is a fix available:

http://lists.openwall.net/linux-kernel/2011/06/21/5

It should be integrated.

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