Re: [Xen-devel] Hit ASSERT in kill_timer function

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 04/30/2014 04:49 PM, Jan Beulich wrote:
>>>> On 30.04.14 at 16:40, <julien.grall@xxxxxxxxxx> wrote:
>> I played a bit with the function vcpu_initialize on ARM.
>> If it fails, it will likely crash Xen with the following stack trace:
>>
>> (XEN) Xen BUG at 
>> /local/home/julien/works/arndale/xen/xen/include/xen/list.h:175
>> ...
>> (XEN) Xen call trace:
>> (XEN)    [<002457e0>] __bug+0x2c/0x44 (PC)
>> (XEN)    [<002457e0>] __bug+0x2c/0x44 (LR)
>> (XEN)    [<00231cb0>] kill_timer+0x1bc/0x364
>> (XEN)    [<002296e4>] sched_destroy_vcpu+0x1c/0x14c
>> (XEN)    [<002081d8>] alloc_vcpu+0x17c/0x270
>> (XEN)    [<00206a10>] do_domctl+0xa74/0x11f4
>> (XEN)    [<00254698>] do_trap_hypervisor+0x7f0/0xb44
>> (XEN)    [<00257110>] return_from_trap+0/0x4
>>
>> It's easily reproductible on ARM with this small patch:
>>
>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>> index ccccb77..7ada03f 100644
>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -473,6 +473,9 @@ int vcpu_initialise(struct vcpu *v)
>>      if ( (rc = vcpu_vtimer_init(v)) != 0 )
>>          return rc;
>>  
>> +    if ( v->domain->domain_id != 0 )
>> +        return -EFAULT;
>> +
>>      return rc;
>>  }
>>
>> I guess we forget to take a lock or smth like that, but I don't know 
>> enough this code.
> 
> I definitely can't reproduce this on x86 - I tried three different
> variations of which vCPU(s) to fail this function on. Are you sure
> you didn't corrupt something with your experiments?

Yes, I've checkout xengit/staging (commit 9f2f129) and applied tiny patch above.

Usually the first iteration I get:

Parsing config from dom1.xl
libxl: error: libxl_dom.c:239:libxl__build_pre: Couldn't set max vcpu count
libxl: error: libxl_create.c:1036:domcreate_rebuild_done: cannot (re-)build 
domain: -3

And then Xen will crash as soon as I try to create another domain.

I will investigate in ARM side to see what happen.

Regards,

-- 
Julien Grall

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