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

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Date:   Fri, 1 Nov 2019 19:19:11 -0200
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        joao.m.martins@...cle.com, rafael.j.wysocki@...el.com,
        rkrcmar@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH 4/5] cpuidle-haltpoll: add a check to ensure grow start
 value is nonzero

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.