Re: qemu-kvm-1.1.0 crashing with kernel 3.5.0-rc6

[Avi Kivity <avi@redhat.com>]

On 07/31/2012 02:36 AM, Marcelo Tosatti wrote:
> 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.

So the same problem should happen with %fs and %gs, no?

x86_64 is safe, since it entry_64.S never saves/restores segment registers.

-- 
error compiling committee.c: too many arguments to function