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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 CF099C31E46 for ; Wed, 12 Jun 2019 08:49:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9E4C2086A for ; Wed, 12 Jun 2019 08:49:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406629AbfFLIt4 (ORCPT ); Wed, 12 Jun 2019 04:49:56 -0400 Received: from foss.arm.com ([217.140.110.172]:47638 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726636AbfFLIt4 (ORCPT ); Wed, 12 Jun 2019 04:49:56 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AE6E82B; Wed, 12 Jun 2019 01:49:55 -0700 (PDT) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8BC543F246; Wed, 12 Jun 2019 01:49:54 -0700 (PDT) Subject: Re: [PATCH v2 1/9] KVM: arm/arm64: vgic: Add LPI translation cache definition From: Julien Thierry To: Marc Zyngier , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Cc: "Raslan, KarimAllah" , "Saidi, Ali" References: <20190611170336.121706-1-marc.zyngier@arm.com> <20190611170336.121706-2-marc.zyngier@arm.com> <54c8547a-51fb-8ae5-975f-261d3934221a@arm.com> Message-ID: <37a7411c-e7e0-e601-b88b-c12e8ebf9861@arm.com> Date: Wed, 12 Jun 2019 09:49:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <54c8547a-51fb-8ae5-975f-261d3934221a@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 12/06/2019 09:16, Julien Thierry wrote: > Hi Marc, > > On 11/06/2019 18:03, Marc Zyngier wrote: [...] >> + >> +void vgic_lpi_translation_cache_init(struct kvm *kvm) >> +{ >> + struct vgic_dist *dist = &kvm->arch.vgic; >> + unsigned int sz; >> + int i; >> + >> + if (!list_empty(&dist->lpi_translation_cache)) >> + return; >> + >> + sz = atomic_read(&kvm->online_vcpus) * LPI_DEFAULT_PCPU_CACHE_SIZE; >> + >> + for (i = 0; i < sz; i++) { >> + struct vgic_translation_cache_entry *cte; >> + >> + /* An allocation failure is not fatal */ >> + cte = kzalloc(sizeof(*cte), GFP_KERNEL); >> + if (WARN_ON(!cte)) >> + break; >> + >> + INIT_LIST_HEAD(&cte->entry); >> + list_add(&cte->entry, &dist->lpi_translation_cache); > > Going through the series, it looks like this list is either empty > (before the cache init) or has a fixed number > (LPI_DEFAULT_PCPU_CACHE_SIZE * nr_cpus) of entries. And the list never > grows nor shrinks throughout the series, so it seems odd to be using a > list here. > > Is there a reason for not using a dynamically allocated array instead of > the list? (does list_move() provide a big perf advantage over swapping > the data from one array entry to another? Or is there some other > facility I am missing? > Scratch that, I realized having the list makes it easier to implement the LRU policy later in the series. -- Julien Thierry