linux-kernel - Re: [PATCH 4/5] cpuidle-haltpoll: add a check to ensure grow start value is nonzero

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Date:   Mon, 11 Nov 2019 14:54:47 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        joao.m.martins@...cle.com, rafael.j.wysocki@...el.com,
        rkrcmar@...hat.com
Subject: Re: [PATCH 4/5] cpuidle-haltpoll: add a check to ensure grow start
 value is nonzero

On 04/11/19 03:56, Zhenzhong Duan wrote:
> 
> On 2019/11/2 5:19, Marcelo Tosatti wrote:
>> On Sat, Oct 26, 2019 at 11:23:58AM +0800, Zhenzhong Duan wrote:
>>> dev->poll_limit_ns could be zeroed in certain cases (e.g. by
>>> guest_halt_poll_shrink). If guest_halt_poll_grow_start is zero,
>>> dev->poll_limit_ns will never be larger than zero.
>>>
>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
>>> ---
>>>   drivers/cpuidle/governors/haltpoll.c | 15 ++++++++++++---
>>>   1 file changed, 12 insertions(+), 3 deletions(-)
>> I would rather disallow setting grow_start to zero rather
>> than silently setting it to one on the back of the user.
> 
> Ok, will do.

Similar to patch 2, I think disabling halt polling is a good behavior if
grow_start = 0.

Paolo