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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 9FF9BC3B186 for ; Mon, 10 Feb 2020 16:26:47 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 597A120733 for ; Mon, 10 Feb 2020 16:26:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="O249n01K" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 597A120733 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=armlinux.org.uk 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 122A74A59B; Mon, 10 Feb 2020 11:26:47 -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=@armlinux.org.uk 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 v2aQem1yeWSy; Mon, 10 Feb 2020 11:26:45 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id EC97F4A800; Mon, 10 Feb 2020 11:26:45 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id EDF834A59B for ; Mon, 10 Feb 2020 11:26:44 -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 T8YPlJdfycXR for ; Mon, 10 Feb 2020 11:26:43 -0500 (EST) Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 67BA14A50F for ; Mon, 10 Feb 2020 11:26:43 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=65bdrIaYUEY07Eg6lahVGNf+sXMz7DgHQPG+97GSzoU=; b=O249n01KJyJmh5v7eoKu72Wxm aT6PtOrlOoyebt8IeMBdWJ+Mc0G34pwCNSbq0pYUPEVnSHE8dOnkTdb88whOVZjCsaHxz+de39iuw yWGdC/Muzm1L1tlo8Yjkn1SETYGGIMiFmXrUylkja4lUEkM0nU9MJ8ufgf5CDc7P0iz1Cwj0bx9rJ /sVJEE2hjddOOmp19LpzoXQL2y7uBEKycflnocOXeWpZIs83p15iLxzw6REUj4m/ovum6O/B7IyuY 8gdPpNCERbJCVPjnCguAIPq7nX4OSUNFDb7Dbgxau52hL0T9rKWjEzNmX5smg1KyJyTM8hvgHvd9N t9gGOlcEw==; Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:38534) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1j1BtO-0007mo-Kh; Mon, 10 Feb 2020 16:26:38 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1j1BtN-00081o-CD; Mon, 10 Feb 2020 16:26:37 +0000 Date: Mon, 10 Feb 2020 16:26:37 +0000 From: Russell King - ARM Linux admin To: Marc Zyngier Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host Message-ID: <20200210162637.GG25745@shell.armlinux.org.uk> References: <20200210141324.21090-1-maz@kernel.org> <20200210162523.GF25745@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200210162523.GF25745@shell.armlinux.org.uk> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Anders Berg , Arnd Bergmann , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu 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 On Mon, Feb 10, 2020 at 04:25:23PM +0000, Russell King - ARM Linux admin wrote: > On Mon, Feb 10, 2020 at 02:13:19PM +0000, Marc Zyngier wrote: > > KVM/arm was merged just over 7 years ago, and has lived a very quiet > > life so far. It mostly works if you're prepared to deal with its > > limitations, it has been a good prototype for the arm64 version, > > but it suffers a few problems: > > > > - It is incomplete (no debug support, no PMU) > > - It hasn't followed any of the architectural evolutions > > - It has zero users (I don't count myself here) > > - It is more and more getting in the way of new arm64 developments > > > > So here it is: unless someone screams and shows that they rely on > > KVM/arm to be maintained upsteam, I'll remove 32bit host support > > form the tree. One of the reasons that makes me confident nobody is > > using it is that I never receive *any* bug report. Yes, it is perfect. > > But if you depend on KVM/arm being available in mainline, please shout. > > It is only very recently that 64-bit ARM has really started to filter > down to people like me, and people like me have setup systems which > use 32-bit VMs under 64-bit hosts (about a year ago now.) In fact, > everything that you presently see for the *.armlinux.org.uk domain now > runs inside several 32-bit ARM VMs under a 64-bit ARM host. > > It isn't perfect; I've found issues with qemu and libvirt. One example > is the rather sub-standard RTC implementation, which means if you > use libvirt's managesave across a host reboot, the guests idea of > time-of-day freezes while it's asleep, and resumes when the guest is > reloaded - resulting in the guests time-of-day being rather wrong, > sometimes to the point that NTP gives up. That becomes very painful > if you use kerberos authentication, where time-of-day is important. > > So, just because you haven't received any bug reports doesn't mean > there aren't any users; there certainly are, there are problems, > but the problems are in places other than the kernel. ... argh, I see, you're not removing 32-bit guest on 64-bit. Ignore the above then. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm