From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18C83C433DB for ; Wed, 6 Jan 2021 02:13:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D103322D50 for ; Wed, 6 Jan 2021 02:13:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726202AbhAFCNj (ORCPT ); Tue, 5 Jan 2021 21:13:39 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:10024 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbhAFCNi (ORCPT ); Tue, 5 Jan 2021 21:13:38 -0500 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4D9XtT5Hf1zj3Vx; Wed, 6 Jan 2021 10:12:01 +0800 (CST) Received: from [10.174.184.196] (10.174.184.196) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.498.0; Wed, 6 Jan 2021 10:12:50 +0800 Subject: Re: [RFC PATCH v2 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side To: Marc Zyngier CC: Eric Auger , Will Deacon , , , , , Alex Williamson , Cornelia Huck , "Lorenzo Pieralisi" , , References: <20210104081613.100-1-lushenming@huawei.com> <20210104081613.100-4-lushenming@huawei.com> <76a7b9cca485dc8157d3be53189eac69@kernel.org> From: Shenming Lu Message-ID: <6b815f0e-d042-2ec6-369a-41a19cd1b9f9@huawei.com> Date: Wed, 6 Jan 2021 10:12:50 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <76a7b9cca485dc8157d3be53189eac69@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.184.196] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2021/1/5 17:25, Marc Zyngier wrote: > On 2021-01-04 08:16, Shenming Lu wrote: >> From: Zenghui Yu >> >> When setting the forwarding path of a VLPI (switch to the HW mode), >> we could also transfer the pending state from irq->pending_latch to >> VPT (especially in migration, the pending states of VLPIs are restored >> into kvm’s vgic first). And we currently send "INT+VSYNC" to trigger >> a VLPI to pending. >> >> Signed-off-by: Zenghui Yu >> Signed-off-by: Shenming Lu >> --- >>  arch/arm64/kvm/vgic/vgic-v4.c | 12 ++++++++++++ >>  1 file changed, 12 insertions(+) >> >> diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c >> index f211a7c32704..7945d6d09cdd 100644 >> --- a/arch/arm64/kvm/vgic/vgic-v4.c >> +++ b/arch/arm64/kvm/vgic/vgic-v4.c >> @@ -454,6 +454,18 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq, >>      irq->host_irq    = virq; >>      atomic_inc(&map.vpe->vlpi_count); >> >> +    /* Transfer pending state */ >> +    ret = irq_set_irqchip_state(irq->host_irq, >> +                    IRQCHIP_STATE_PENDING, >> +                    irq->pending_latch); >> +    WARN_RATELIMIT(ret, "IRQ %d", irq->host_irq); > > Why do this if pending_latch is 0, which is likely to be > the overwhelming case? Yes, there is no need to do this if pending_latch is 0. > >> + >> +    /* >> +     * Let it be pruned from ap_list later and don't bother >> +     * the List Register. >> +     */ >> +    irq->pending_latch = false; > > What guarantees the pruning? Pruning only happens on vcpu exit, > which means we may have the same interrupt via both the LR and > the stream interface, which I don't believe is legal (it is > like having two LRs holding the same interrupt). Since the irq's pending_latch is set to false here, it will not be populated to the LR in vgic_flush_lr_state() (vgic_target_oracle() will return NULL). > >> + >>  out: >>      mutex_unlock(&its->its_lock); >>      return ret; > > Thanks, > >         M.