From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heyi Guo Subject: Re: [RFC] Question about enable doorbell irq and halt_poll process Date: Wed, 20 Mar 2019 22:31:36 +0800 Message-ID: References: <0fb3c9ba-8428-ea6c-2973-952624f601cc@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0fb3c9ba-8428-ea6c-2973-952624f601cc@huawei.com> Sender: linux-kernel-owner@vger.kernel.org To: "Tangnianyao (ICT)" , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, Linuxarm Cc: wanghaibin.wang@huawei.com, Marc Zyngier , Christoffer Dall List-Id: kvmarm@lists.cs.columbia.edu +cc Marc and Christoffer... On 2019/3/19 21:25, Tangnianyao (ICT) wrote: > Hi, all > > Using gicv4, when guest is waiting for irq, it sends wfi and traps to kvm. > When vlpi is forwarded to PE after its_vpe_deschedule, before halt_poll in > kvm_vcpu_block, halt_poll may increase latency for this vlpi getting to guest. > In halt_poll process, it checks if there's pending irq for vcpu using pending_last. > However, doorbell is not enable at this moment and vlpi or doorbell can not set > pending_last true, to stop halt_poll. It will run until halt_poll time ends, if > there's no other physical irq coming in the meantime. And then vcpu is scheduled out. > This pending vlpi has to wait for vcpu getting schedule in next time. > > Should we enable doorbell before halt_poll process ? > > > . >