From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: qemu-kvm-1.1.0 crashing with kernel 3.5.0-rc6
Date: Mon, 30 Jul 2012 20:36:16 -0300
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Cc: Chris Clayton <chris2553@googlemail.com>,
	Gleb Natapov <gleb@redhat.com>,
	Eric Northup <digitaleric@google.com>, kvm@vger.kernel.org,
	Jan Kiszka <jan.kiszka@siemens.com>
To: Avi Kivity <avi@redhat.com>
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On Mon, Jul 30, 2012 at 07:39:31PM +0300, Avi Kivity wrote:
> On 07/30/2012 05:07 PM, Chris Clayton wrote:
> >>
> >>>> With kernel 3.5.0 with b2da15ac26a0c00 reverted, I have just had 15
> >>>> clean invocations of vanilla qemu-kvm-1.1.1. So that commit would seem
> >>>> to be the problem.
> >>>
> >>> Just to be sure, I've run some more tests today. No crashes occurred in
> >>> 20 runs of vanilla qemu-kvm-1.1.1 on kernel 3.5.0 with b2da15ac26a0c00
> >>> reverted.
> >>
> >> Ok.  I'm trying to reproduce it here on a nested-virt setup, since the
> >> code looks correct.
> >>
> >> What's your preemption settings?
> >>
> >>
> > [chris:~/kernel/linux-3.5.0]$ grep PREEMPT .config
> > CONFIG_TREE_PREEMPT_RCU=y
> > CONFIG_PREEMPT_RCU=y
> > CONFIG_PREEMPT_NOTIFIERS=y
> > # CONFIG_PREEMPT_NONE is not set
> > # CONFIG_PREEMPT_VOLUNTARY is not set
> > CONFIG_PREEMPT=y
> > CONFIG_PREEMPT_COUNT=y
> 
> Here's what I think that is happening
> 
>   vcpu_load
>   ...
>   vmx_save_host_state
>   vmx_vcpu_run
>   (ds.cpl, es.cpl cleared by hardware)
> 
>   interrupt
>     push ds, es  # pushes bad ds, es
>     schedule
>       vmx_vcpu_put
>         vmx_load_host_state
>           reload ds, es
>     pop ds, es  # of other thread's stack
>     iret
>   # other thread runs
>   interrupt
>     schedule  # back in vcpu thread
>     interrupt return: pop ds, es  # <-- problem
>     iret
> 
>    ...
>    vcpu_put
> 
>    # bad ds, es, but !vmx->host_state.loaded
> 
> Marcelo, did I miss something here?

Don't think so.

> 
> Unfortunately, my reproducer has ceased to reproduce.  But the fix is
> easy if the analysis above is right.
> 
> -- 
> error compiling committee.c: too many arguments to function
>