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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 81431C4320E for ; Thu, 26 Aug 2021 12:26:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63D0B61076 for ; Thu, 26 Aug 2021 12:26:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241404AbhHZM1C (ORCPT ); Thu, 26 Aug 2021 08:27:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28266 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241041AbhHZM1B (ORCPT ); Thu, 26 Aug 2021 08:27:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629980773; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=S+Sat3y8UXxpfnh9XHhnKb0JrTjNlFz93a/rQHz2hnA=; b=EOBhHZShWa+BYcOkImcVpT6aB/Ctqnc3njxm8wgvsUd7ulxSpTvAzFQikzoiBHjew03rtE R5SwED6trYAKqN0O/HCLTKF2S9XVOe8a0kLiugmhR4//8x4FbV44/hKnc860AryVUOh49S PZyqFc1dGTxP1fKCC5j0RxAnI5ny18w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-9-QOCx3-xGPV2EIvDk0cMz8A-1; Thu, 26 Aug 2021 08:25:07 -0400 X-MC-Unique: QOCx3-xGPV2EIvDk0cMz8A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EA3691008066; Thu, 26 Aug 2021 12:25:05 +0000 (UTC) Received: from vitty.brq.redhat.com (unknown [10.40.193.115]) by smtp.corp.redhat.com (Postfix) with ESMTP id 671E060936; Thu, 26 Aug 2021 12:25:00 +0000 (UTC) From: Vitaly Kuznetsov To: kvm@vger.kernel.org, Paolo Bonzini Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , "Dr. David Alan Gilbert" , Nitesh Narayan Lal , Lai Jiangshan , linux-kernel@vger.kernel.org Subject: [PATCH v3 3/4] KVM: Optimize kvm_make_vcpus_request_mask() a bit Date: Thu, 26 Aug 2021 14:24:41 +0200 Message-Id: <20210826122442.966977-4-vkuznets@redhat.com> In-Reply-To: <20210826122442.966977-1-vkuznets@redhat.com> References: <20210826122442.966977-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Iterating over set bits in 'vcpu_bitmap' should be faster than going through all vCPUs, especially when just a few bits are set. Signed-off-by: Vitaly Kuznetsov --- virt/kvm/kvm_main.c | 83 ++++++++++++++++++++++++++------------------- 1 file changed, 49 insertions(+), 34 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2082aceffbf6..5d2b1f0fafaf 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -261,49 +261,64 @@ static inline bool kvm_kick_many_cpus(cpumask_var_t tmp, bool wait) return true; } +static void kvm_make_vcpu_request(struct kvm *kvm, struct kvm_vcpu *vcpu, + unsigned int req, cpumask_var_t tmp, + int current_cpu) +{ + int cpu = vcpu->cpu; + + kvm_make_request(req, vcpu); + + if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu)) + return; + + /* + * tmp can be "unavailable" if cpumasks are allocated off stack as + * allocation of the mask is deliberately not fatal and is handled by + * falling back to kicking all online CPUs. + */ + if (!cpumask_available(tmp)) + return; + + /* + * Note, the vCPU could get migrated to a different pCPU at any point + * after kvm_request_needs_ipi(), which could result in sending an IPI + * to the previous pCPU. But, that's OK because the purpose of the IPI + * is to ensure the vCPU returns to OUTSIDE_GUEST_MODE, which is + * satisfied if the vCPU migrates. Entering READING_SHADOW_PAGE_TABLES + * after this point is also OK, as the requirement is only that KVM wait + * for vCPUs that were reading SPTEs _before_ any changes were + * finalized. See kvm_vcpu_kick() for more details on handling requests. + */ + if (kvm_request_needs_ipi(vcpu, req)) { + cpu = READ_ONCE(vcpu->cpu); + if (cpu != -1 && cpu != current_cpu) + __cpumask_set_cpu(cpu, tmp); + } +} + bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req, struct kvm_vcpu *except, unsigned long *vcpu_bitmap, cpumask_var_t tmp) { - int i, cpu, me; + int i, me; struct kvm_vcpu *vcpu; bool called; me = get_cpu(); - kvm_for_each_vcpu(i, vcpu, kvm) { - if ((vcpu_bitmap && !test_bit(i, vcpu_bitmap)) || - vcpu == except) - continue; - - kvm_make_request(req, vcpu); - - if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu)) - continue; - - /* - * tmp can be "unavailable" if cpumasks are allocated off stack - * as allocation of the mask is deliberately not fatal and is - * handled by falling back to kicking all online CPUs. - */ - if (!cpumask_available(tmp)) - continue; - - /* - * Note, the vCPU could get migrated to a different pCPU at any - * point after kvm_request_needs_ipi(), which could result in - * sending an IPI to the previous pCPU. But, that's ok because - * the purpose of the IPI is to ensure the vCPU returns to - * OUTSIDE_GUEST_MODE, which is satisfied if the vCPU migrates. - * Entering READING_SHADOW_PAGE_TABLES after this point is also - * ok, as the requirement is only that KVM wait for vCPUs that - * were reading SPTEs _before_ any changes were finalized. See - * kvm_vcpu_kick() for more details on handling requests. - */ - if (kvm_request_needs_ipi(vcpu, req)) { - cpu = READ_ONCE(vcpu->cpu); - if (cpu != -1 && cpu != me) - __cpumask_set_cpu(cpu, tmp); + if (vcpu_bitmap) { + for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) { + vcpu = kvm_get_vcpu(kvm, i); + if (!vcpu || vcpu == except) + continue; + kvm_make_vcpu_request(kvm, vcpu, req, tmp, me); + } + } else { + kvm_for_each_vcpu(i, vcpu, kvm) { + if (vcpu == except) + continue; + kvm_make_vcpu_request(kvm, vcpu, req, tmp, me); } } -- 2.31.1