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Re: [PATCH] xen: Modify domain_crash() to take a print string


  • To: Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>
  • From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
  • Date: Thu, 3 Feb 2022 14:41:21 +0000
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  • Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, "Stefano Stabellini" <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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  • Thread-topic: [PATCH] xen: Modify domain_crash() to take a print string

On 03/02/2022 14:19, Jan Beulich wrote:
> On 03.02.2022 15:11, Andrew Cooper wrote:
>> On 03/02/2022 13:48, Julien Grall wrote:
>>> On 03/02/2022 13:38, Andrew Cooper wrote:
>>>> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
>>>> index 37f78cc4c4c9..38b390d20371 100644
>>>> --- a/xen/include/xen/sched.h
>>>> +++ b/xen/include/xen/sched.h
>>>> @@ -736,10 +736,15 @@ void vcpu_end_shutdown_deferral(struct vcpu *v);
>>>>    * from any processor.
>>>>    */
>>>>   void __domain_crash(struct domain *d);
>>>> -#define domain_crash(d) do
>>>> {                                              \
>>>> -    printk("domain_crash called from %s:%d\n", __FILE__,
>>>> __LINE__);       \
>>>> -   
>>>> __domain_crash(d);                                                    \
>>>> -} while (0)
>>>> +#define domain_crash(d, ...)                            \
>>>> +    do {                                                \
>>>> +        if ( count_args(__VA_ARGS__) == 0 )             \
>>>> +            printk("domain_crash called from %s:%d\n",  \
>>>> +                   __FILE__, __LINE__);                 \
>>> I find a bit odd that here you are using a normal printk
>> That's unmodified from before.  Only reformatted.
>>
>>> but...
>>>
>>>
>>>> +        else                                            \
>>>> +            printk(XENLOG_G_ERR __VA_ARGS__);           \
>>> here it is XENLOG_G_ERR. In fact, isn't it ratelimited? If so,
>>> wouldn't it be better to only use XENLOG_ERR so they can always be
>>> seen? (A domain shouldn't be able to abuse it).
>> Perhaps.  I suppose it is more important information than pretty much
>> anything else about the guest.
> Indeed, but then - is this really an error in all cases?

Yes.  It is always a fatal event for the VM.

> The prior
> printk() simply ended up defaulting to a warning, and I would think
> that's what the new one should be doing too.

WARNING isn't exactly correct for a fatal event.

Ideally, we want a non-ratelimited G_ERR, but that doesn't exist.  If it
appears in the future, we can use it.

The set of people running with loglvl=error is almost certainly empty,
so it doesn't matter.

~Andrew

 


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