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=DKIM_INVALID,DKIM_SIGNED, 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 72D69C33CB1 for ; Wed, 15 Jan 2020 13:51:14 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 27846214AF for ; Wed, 15 Jan 2020 13:51:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="LAyFnhrY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 27846214AF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D24C64B165; Wed, 15 Jan 2020 08:51:13 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 54dcQ4hDlgPu; Wed, 15 Jan 2020 08:51:08 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 9713A4B159; Wed, 15 Jan 2020 08:51:08 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6B5DC4B0ED for ; Wed, 15 Jan 2020 08:51:07 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id SfiDmrQtB8rp for ; Wed, 15 Jan 2020 08:51:01 -0500 (EST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 5603F4B133 for ; Wed, 15 Jan 2020 08:51:01 -0500 (EST) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4CC8F222C3; Wed, 15 Jan 2020 13:51:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579096260; bh=zgFuK23PelupfMFWwsdmgHynqFy4M+em1nBsFleJZmg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=LAyFnhrYoxuHERN9eMwwCXKbcwce1ikeoXzQMYJ74XKiwgWrr6oFP5V8F0t9Iz2LZ VekcCt7rJD5+YiS3BH8kQejmTn5hHK22RyMp4//taH94ffYDsAnEhnnaEPVVrmzOc+ FlCFXOQ9i6ZZd+WPBBXL6pPuOGqDNxX12lmgIV3k= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1irj4U-0000G6-KS; Wed, 15 Jan 2020 13:50:58 +0000 MIME-Version: 1.0 Date: Wed, 15 Jan 2020 13:50:58 +0000 From: Marc Zyngier To: Shaokun Zhang Subject: Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation In-Reply-To: References: Message-ID: <37126a877e1160ed50ee6d95a03d1574@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.8 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: zhangshaokun@hisilicon.com, tangnianyao@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, fanhenglong@huawei.com, wanghaibin.wang@huawei.com, lizixian@hisilicon.com, wangwudi@hisilicon.com, jiayanlei@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: wangwudi , Lizixian , jiayanlei@huawei.com, fanhenglong@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Shaokun, On 2020-01-14 14:20, Shaokun Zhang wrote: > Hi Marc, > > On activation, VMAPP command is followed by a VINVALL, which could be > quite expensive for the start-up of virtual machine. If a vpeid is > allowed > successfully, it is not used in system. How expensive? This is exactly similar to what happens on a physical machine where we perform an INVALL on MAPC. And yet you don't complain about that. Please provide numbers. > We may consider put VINVALL to deactivation to ensure all cache of > certain > vpeid is invalid, to simplify activation. We consider start-up may be > more > common and more time-consuming-sensitive than shutdown process. In my world, they cost the same thing, and happen just as often. Also, I want guarantees that on VMAPP, there is no stale information even if this is the first time we're using this VPEid (who knows what happens over kexec, for example). > Do you think it's all right? I don't, for the reasons stated above. You also provide no numbers showing how bad the overhead is, so I'm left guessing. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm