Re: [PATCH 1/3] sched: better handling for busy polling loops

[Paolo Bonzini]

On 23/10/20 09:19, Peter Zijlstra wrote:
>> +	/*
>> +	 * preemption needs to be kept disabled between prepare_to_busy_poll()
>> +	 * and end_busy_poll().
>> +	 */
>> +	BUG_ON(preemptible());
>> +	if (allow_resched)
>> +		preempt_enable();
>> +	else
>> +		preempt_enable_no_resched();
> NAK on @allow_resched
> 

Since KVM is the one passing false, indeed I see no reason for the
argument; you can just use preempt_enable().  There is no impact for
example on the tracking of how much time was spent polling; that
ktime_get() for the end of the polling period is done before calling
end_busy_poll().

Paolo