linux-kernel - Re: kvm hangs w/o nolapic

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Date:	Fri, 20 Nov 2009 21:18:15 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	kvm <kvm@...r.kernel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yhlu.kernel@...il.com>, Ingo Molnar <mingo@...e.hu>
Subject: Re: kvm hangs w/o nolapic

On Fri, Nov 20, 2009 at 12:11:55PM +0100, Johannes Berg wrote:
> My 2.6.32-rc7 kvm (both guest+host, x86_64) hangs w/o "nolapic" here:
> 
>   while (lapic_cal_loops <= LAPIC_CAL_LOOPS)
>      cpu_relax();
> 
> because lapic_cal_loops never changes from -1.
> 
> Code was last changed by
> commit 2f04fa888d270951b9e0fe9e641ddd560d77ad1b
> Author: Yinghai Lu <yhlu.kernel@...il.com>
> Date:   Sun Aug 24 02:01:54 2008 -0700
> 
>     x86: apic copy calibrate_APIC_clock to each other in apic_32/64.c
> 
> but I haven't tested reverting that.
> 
> johannes

Hi Johannes,

It will be not easy to revert since the commit was "preparing to merge"
apic_32/64.c. It rather seems there is a problem with timer(s) other then
APIC's one (ie PIT, HPET, PM). And since you're under kvm -- it could be
a corner case as well.

I've just booted a latest -tip with kvm without problems.
I've been using

|
| QEMU PC emulator version 0.9.1 (kvm-84)
|

Perhaps you could capture console with "debug apic=debug") and to gather
more info? And .config?

	-- Cyrill
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