From patchwork Mon Aug 21 20:35:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= X-Patchwork-Id: 804165 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=kvm-ppc-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3xblvP0Ky0z9t2R for ; Tue, 22 Aug 2017 06:40:49 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754246AbdHUUiG (ORCPT ); Mon, 21 Aug 2017 16:38:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48650 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753739AbdHUUiE (ORCPT ); Mon, 21 Aug 2017 16:38:04 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 63EB3C047B8C; Mon, 21 Aug 2017 20:38:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 63EB3C047B8C Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=rkrcmar@redhat.com Received: from flask (unknown [10.43.2.80]) by smtp.corp.redhat.com (Postfix) with SMTP id F1C8B5CC21; Mon, 21 Aug 2017 20:37:58 +0000 (UTC) Received: by flask (sSMTP sendmail emulation); Mon, 21 Aug 2017 22:37:58 +0200 From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-mips@linux-mips.org, kvm-ppc@vger.kernel.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Paolo Bonzini , David Hildenbrand , Christoffer Dall , Marc Zyngier , Christian Borntraeger , Cornelia Huck , James Hogan , Paul Mackerras , Alexander Graf Subject: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started vcpus Date: Mon, 21 Aug 2017 22:35:22 +0200 Message-Id: <20170821203530.9266-2-rkrcmar@redhat.com> In-Reply-To: <20170821203530.9266-1-rkrcmar@redhat.com> References: <20170821203530.9266-1-rkrcmar@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 21 Aug 2017 20:38:04 +0000 (UTC) Sender: kvm-ppc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org We can add a variable instead of scanning all online VCPUs to know how many are started. We can't trivially tell which VCPU is the last one, though. Suggested-by: Cornelia Huck Signed-off-by: Radim Krčmář --- arch/s390/include/asm/kvm_host.h | 1 + arch/s390/kvm/kvm-s390.c | 39 +++++++++++++++------------------------ 2 files changed, 16 insertions(+), 24 deletions(-) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index a409d5991934..be0d0bdf585b 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -735,6 +735,7 @@ struct kvm_arch{ struct mutex ipte_mutex; struct ratelimit_state sthyi_limit; spinlock_t start_stop_lock; + unsigned started_vcpus; struct sie_page2 *sie_page2; struct kvm_s390_cpu_model model; struct kvm_s390_crypto crypto; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 9f23a9e81a91..1534778a3c66 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -3414,25 +3414,17 @@ static void __enable_ibs_on_vcpu(struct kvm_vcpu *vcpu) void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu) { - int i, online_vcpus, started_vcpus = 0; - if (!is_vcpu_stopped(vcpu)) return; trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 1); /* Only one cpu at a time may enter/leave the STOPPED state. */ spin_lock(&vcpu->kvm->arch.start_stop_lock); - online_vcpus = atomic_read(&vcpu->kvm->online_vcpus); - for (i = 0; i < online_vcpus; i++) { - if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) - started_vcpus++; - } - - if (started_vcpus == 0) { + if (vcpu->kvm->arch.started_vcpus == 0) { /* we're the only active VCPU -> speed it up */ __enable_ibs_on_vcpu(vcpu); - } else if (started_vcpus == 1) { + } else if (vcpu->kvm->arch.started_vcpus == 1) { /* * As we are starting a second VCPU, we have to disable * the IBS facility on all VCPUs to remove potentially @@ -3441,6 +3433,8 @@ void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu) __disable_ibs_on_all_vcpus(vcpu->kvm); } + vcpu->kvm->arch.started_vcpus++; + atomic_andnot(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags); /* * Another VCPU might have used IBS while we were offline. @@ -3453,16 +3447,12 @@ void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu) void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu) { - int i, online_vcpus, started_vcpus = 0; - struct kvm_vcpu *started_vcpu = NULL; - if (is_vcpu_stopped(vcpu)) return; trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 0); /* Only one cpu at a time may enter/leave the STOPPED state. */ spin_lock(&vcpu->kvm->arch.start_stop_lock); - online_vcpus = atomic_read(&vcpu->kvm->online_vcpus); /* SIGP STOP and SIGP STOP AND STORE STATUS has been fully processed */ kvm_s390_clear_stop_irq(vcpu); @@ -3470,19 +3460,20 @@ void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu) atomic_or(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags); __disable_ibs_on_vcpu(vcpu); - for (i = 0; i < online_vcpus; i++) { - if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) { - started_vcpus++; - started_vcpu = vcpu->kvm->vcpus[i]; - } - } + vcpu->kvm->arch.started_vcpus--; + + if (vcpu->kvm->arch.started_vcpus == 1) { + struct kvm_vcpu *started_vcpu; - if (started_vcpus == 1) { /* - * As we only have one VCPU left, we want to enable the - * IBS facility for that VCPU to speed it up. + * As we only have one VCPU left, we want to enable the IBS + * facility for that VCPU to speed it up. */ - __enable_ibs_on_vcpu(started_vcpu); + kvm_for_each_vcpu(i, started_vcpu, vcpu->kvm) + if (!is_vcpu_stopped(started_vcpu)) { + __enable_ibs_on_vcpu(started_vcpu); + break; + } } spin_unlock(&vcpu->kvm->arch.start_stop_lock);