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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 BB8F4C33CB1 for ; Thu, 16 Jan 2020 06:22:10 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 44ABB2081E for ; Thu, 16 Jan 2020 06:22:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 44ABB2081E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hisilicon.com 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 B40704B10E; Thu, 16 Jan 2020 01:22:09 -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 aMttFSL9rEbs; Thu, 16 Jan 2020 01:22:05 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id BB3374B10F; Thu, 16 Jan 2020 01:22:05 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C8B324B10F for ; Thu, 16 Jan 2020 01:22:04 -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 P8ie0GuAdmFa for ; Thu, 16 Jan 2020 01:22:00 -0500 (EST) Received: from huawei.com (szxga06-in.huawei.com [45.249.212.32]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 080274B10E for ; Thu, 16 Jan 2020 01:21:59 -0500 (EST) Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id BD99A811C5DD757182DD; Thu, 16 Jan 2020 14:21:56 +0800 (CST) Received: from [127.0.0.1] (10.74.221.148) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.439.0; Thu, 16 Jan 2020 14:21:50 +0800 Subject: Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation To: Marc Zyngier References: <37126a877e1160ed50ee6d95a03d1574@kernel.org> From: Shaokun Zhang Message-ID: Date: Thu, 16 Jan 2020 14:21:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <37126a877e1160ed50ee6d95a03d1574@kernel.org> X-Originating-IP: [10.74.221.148] X-CFilter-Loop: Reflected 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Marc, On 2020/1/15 21:50, Marc Zyngier wrote: > 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. > Agree, I didn't consider this before. > 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. > Got it, you are right :-). Thanks for your explaination Shaokun > Thanks, > > M. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm