Re: [PATCH 2/5] xen/sched: rtds: enforce admission control in xl sched-rtds

[Furkan Çalışkan <frn1furkan10@xxxxxxxxx>]

On 9/18/26 10:46, Jürgen Groß wrote:
> On 14.09.26 12:40, Furkan Çalışkan wrote:
>>
>> On 9/14/26 12:16, Juergen Gross wrote:
>>> On 26.08.26 06:57, Furkan Caliskan wrote:
>>>> Now that we have introduced admission control for new and
>>>> removed units. Extend it to XEN_DOMCTL_SCHEDOP_putinfo and
>>>> putvcpuinfo, so growing an existing reservation via
>>>> xl sched-rtds is checked too.
>>>>
>>>> putinfo sets the same (period, budget) for every unit of a
>>>> domain at once, so it tests the whole domain's utilization
>>>> delta atomically, rather than unit-by-unit, which could
>>>> spuriously reject an overall-acceptable change depending on
>>>> iteration order.
>>>>
>>>> putvcpuinfo changes one unit at a time, so it just calls
>>>> rt_admission_test() directly.
>>>>
>>>> Signed-off-by: Furkan Caliskan <frn1furkan10@xxxxxxxxx>
>>>> ---
>>>>    xen/common/sched/rt.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>>>>    1 file changed, 42 insertions(+)
>>>>
>>>> diff --git a/xen/common/sched/rt.c b/xen/common/sched/rt.c
>>>> index 9126320801..9643a277fe 100644
>>>> --- a/xen/common/sched/rt.c
>>>> +++ b/xen/common/sched/rt.c
>>>> @@ -1527,11 +1527,43 @@ rt_dom_cntl(
>>>>            op->u.rtds.budget = RTDS_DEFAULT_BUDGET / MICROSECS(1);
>>>>            break;
>>>>        case XEN_DOMCTL_SCHEDOP_putinfo:
>>>> +    {
>>>> +        uint64_t dom_old_util = 0, new_util, new_total;
>>>> +        unsigned int nr_units = 0;
>>>> +
>>>>            rc = rt_validate_params(&op->u.rtds, &period, &budget);
>>>>            if ( rc )
>>>>                break;
>>>>    +        new_util = rt_unit_utilization(period, budget);
>>>> +
>>>>            spin_lock_irqsave(&prv->lock, flags);
>>>> +
>>>> +        /*
>>>> +         * Same (period, budget) for every unit of d: test and commit
>>>> +         * the domain's whole utilization delta atomically, rather
>>>> +         * than unit-by-unit, which could spuriously reject an
>>>> +         * overall-acceptable change depending on iteration order.
>>>> +         */
>>>> +        for_each_sched_unit ( d, unit )
>>>> +        {
>>>> +            svc = rt_unit(unit);
>>>> +            dom_old_util += rt_unit_utilization(svc->period, svc->budget);
>>>> +            nr_units++;
>>>> +        }
>>>> +
>>>> +        new_total = prv->utilization - dom_old_util +
>>>> +                    (uint64_t)nr_units * new_util;
>>>> +
>>>> +        if ( new_total > prv->utilization && new_total > 
>>>> rt_utilization_cap(d) )
>>>> +        {
>>>> +            rc = -EINVAL;
>>>
>>> Is EINVAL a good choice here? I think a different error code might be 
>>> wanted.
>>
>> Would EBUSY be okay here? Or what else would you suggest?
> 
> EBUSY is a liitle bit better. What do you think about ENOSPC?
> 
> 
> Juergen

ENOSPC sounds good to me, I'll go with that.

Thanks,

Furkan