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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 4CC09C433B4 for ; Sun, 16 May 2021 16:16:08 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CA8DF610A7 for ; Sun, 16 May 2021 16:16:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA8DF610A7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47712 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1liJR0-0003HI-P4 for qemu-devel@archiver.kernel.org; Sun, 16 May 2021 12:16:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56736) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1liJO2-0000xT-P8 for qemu-devel@nongnu.org; Sun, 16 May 2021 12:13:02 -0400 Received: from mail-ej1-x62c.google.com ([2a00:1450:4864:20::62c]:40912) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1liJO0-00057n-AN for qemu-devel@nongnu.org; Sun, 16 May 2021 12:13:02 -0400 Received: by mail-ej1-x62c.google.com with SMTP id n2so5607380ejy.7 for ; Sun, 16 May 2021 09:12:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XoynUOz4+iGXyLuogrv4pHtuE2PMOYr63gAjwTVd2q4=; b=BA/GkLx4jnQQ+zgByJrsCweIkoElvRx0DRrTU3WPTN+0whSnZiS4s89bsRISrk9rIL /5RtoMxty21ubEqESgoCICf55UHpbTlpKhRN5Xo2mmbGX68Mm6r41LASOlApV023v/R2 X0dBnDz5uWD427v3JCWnkdzkaikbMT6BIN0LP4N+s/ZE3xKSEMRGnjic1v2ZMTznTSG5 SDValxT9wwatQuIWwIBOmZpnPF0Y07treflNoV4xHzQo8FrT2z4Sc5+sG6yv0YctZxFW 1RMqGXyFSlDiGqD/7NOUUQJYxNZnDqqbjdiAbN6Jcyhj5kzmPyTY0GLN3HYSsM0JnJlC i3vg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=XoynUOz4+iGXyLuogrv4pHtuE2PMOYr63gAjwTVd2q4=; b=WeFUiX5lAIPz4n8HCtkuq5swX9PPr0aJsqHU/vN7WPJPa4F5GGUeenEum8rr5mE5Ea 2wUwNWyrAp7zlBTDC+TsGdmRDtz2Gh8CXY22tgHE4YV7wYYpbDTYdmGr2WAD7Rrqot/X 6BJs3JoHJ5P806w2KOhNZmC2KN6groLAvX2RkCEe+m2x4Uvt2aneHO2rInxAU7ZgeZQs XGmChaZTHM/7vvRxOY9nu8zRRTK3vyaXHR7qf4kPjxbpGpzjQaiiBTBKP3iwQELNFNMk PRuHAcUe59tWfFTqxWLEXXWwAmKe3HYheFT3LJhWL2H0DXUiyQHoSLfk5JoU4qfZ71m+ MFyw== X-Gm-Message-State: AOAM530uf0gKaW5uZOT0ZPMStlIA2/q7KgEFIoY7ERrtKby1jZ9oiWAl aGe0xjLxktf92uh05VjoKYpP6XuWUA3eaqUYLHdKtQ== X-Google-Smtp-Source: ABdhPJwBg5uIgiYmDli3hIr8YmTR9mdjHjbNEzyKS9ORKbVxcMc3+edHT8vcj0vnZJkYgmVDFHEz78JIPWwdyc6hH+k= X-Received: by 2002:a17:906:9bd6:: with SMTP id de22mr9580474ejc.382.1621181578707; Sun, 16 May 2021 09:12:58 -0700 (PDT) MIME-Version: 1.0 References: <20210120224444.71840-1-agraf@csgraf.de> <20210120224444.71840-12-agraf@csgraf.de> <223c7fbc-3a07-e97c-04eb-ef38ec3d67fe@csgraf.de> In-Reply-To: <223c7fbc-3a07-e97c-04eb-ef38ec3d67fe@csgraf.de> From: Peter Maydell Date: Sun, 16 May 2021 17:12:44 +0100 Message-ID: Subject: Re: [PATCH v6 11/11] hvf: arm: Implement -cpu host To: Alexander Graf Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2a00:1450:4864:20::62c; envelope-from=peter.maydell@linaro.org; helo=mail-ej1-x62c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , Richard Henderson , QEMU Developers , Cameron Esfahani , Roman Bolshakov , qemu-arm , Frank Yang , Paolo Bonzini , Peter Collingbourne Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sun, 16 May 2021 at 12:16, Alexander Graf wrote: > > > On 28.01.21 17:55, Peter Maydell wrote: > > Nicer to follow the KVM approach of only doing this once > > and caching the results in arm_host_cpu_features, so that > > for a many-cores VM you don't do it once per core. > > > I tend to disagree. This scales nicely with the number of cores you have > in the system and it's blazingly fast :). I would rather like to > optimize for simplicity here. How does "do something once per vCPU" scale better than "do something once when QEMU starts" ?? I would prefer to optimise for "don't be unnecessarily different from how we do stuff with KVM", please. thanks -- PMM