linux-kernel - Re: [PATCH] xen: initialize xen panic handler for PVHVM

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Message-ID: <5211851E.4010903@oracle.com>
Date:	Mon, 19 Aug 2013 10:38:22 +0800
From:	vaughan <vaughan.cao@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	jeremy@...p.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen: initialize xen panic handler for PVHVM

On 08/16/2013 08:43 PM, Konrad Rzeszutek Wilk wrote:
> On Fri, Aug 16, 2013 at 04:10:56PM +0800, Vaughan Cao wrote:
>> kernel use callback linked in panic_notifier_list to notice others when panic
>> happens.
>> NORET_TYPE void panic(const char * fmt, ...){
>>     ...
>>     atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
>> }
>> When xen aware this, it will call xen_reboot(SHUTDOWN_crash) to send out an
>   ^^^^^^^^^^^^^^^^^^^-> "When Xen becomes aware of this"
>
>> event with reason code - SHUTDOWN_crash.
>> xen_panic_handler_init() is defined to register on panic_notifier_list but
>> we only call it in xen_arch_setup which only be called by pvm, this patch is
>                                           ^^^^^^^-> "is only"
>>  necessary for pvhvm.
> Could you tell me what has been happening without this patch?
Setting 'on_crash=coredump-restart' in PVHVM guest config file can't
lead a vmcore to be generate when the guest panics. It can be reproduced
with 'echo c > /proc/sysrq-trigger'.
>From the xend.log, we find the reason code gotten by dominfo is not as
expected:
  [2013-07-29 08:55:37 19378] INFO (XendDomainInfo:2148) Domain has
shutdown: name=oakDom1 id=15 reason=reboot.
While log from a guest who can capture the crash is as below:   
  [2013-07-29 08:13:42 19378] WARNING (XendDomainInfo:2131) Domain has
crashed: name=oakDom1 id=14.

Thanks,
Vaughan
>
> Thank you.
>
>> Signed-off-by: Vaughan Cao <vaughan.cao@...cle.com>
>> ---
>>  arch/x86/xen/enlighten.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
>> index 4aec5ed..53e5726 100644
>> --- a/arch/x86/xen/enlighten.c
>> +++ b/arch/x86/xen/enlighten.c
>> @@ -1713,6 +1713,8 @@ static void __init xen_hvm_guest_init(void)
>>  
>>  	xen_hvm_init_shared_info();
>>  
>> +	xen_panic_handler_init();
>> +
>>  	if (xen_feature(XENFEAT_hvm_callback_vector))
>>  		xen_have_vector_callback = 1;
>>  	xen_hvm_smp_init();
>> -- 
>> 1.7.11.7
>>

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