Re: [PATCH v6 for Xen 4.7 1/4] xen: enable per-VCPU parameter settings for RTDS scheduler

[Chong Li <lichong659@gmail.com>]

On Tue, Mar 8, 2016 at 1:09 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> On Sun, Mar 06, 2016 at 11:55:55AM -0600, Chong Li wrote:
> [...]
>> @@ -1163,6 +1173,96 @@ rt_dom_cntl(
>>          }
>>          spin_unlock_irqrestore(&prv->lock, flags);
>>          break;
>> +    case XEN_DOMCTL_SCHEDOP_getvcpuinfo:

>> +
>> +            period = MICROSECS(local_sched.s.rtds.period);
>> +            budget = MICROSECS(local_sched.s.rtds.budget);
>> +            if ( period > RTDS_MAX_PERIOD || budget < RTDS_MIN_BUDGET ||
>> +                          budget > period || period < RTDS_MIN_PERIOD )
>> +            {
>> +                rc = -EINVAL;
>> +                break;
>> +            }
>> +
>> +            /*
>> +             * We accept period/budget less than 100 us, but will warn users about
>> +             * the large scheduling overhead due to it
>> +             */
>> +            if ( period < MICROSECS(100) || budget < MICROSECS(100) )
>> +                printk("Warning: period or budget set to less than 100us.\n"
>> +                       "This may result in high scheduling overhead.\n");
>> +
>
> I'm not the maintainer, but I think having printk here is bad idea
> because the toolstack can then DoS the hypervisor.
>
>
> Wei.

So what function should I use here? I see many LOG() calls in libxl,
but I'm not sure whether that can be used here.

Chong


-- 
Chong Li
Department of Computer Science and Engineering
Washington University in St.louis

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