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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 B89BBC11D07 for ; Thu, 20 Feb 2020 14:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E537208C4 for ; Thu, 20 Feb 2020 14:01:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582207297; bh=PeA7JgpdUfYYu08f+gwb07KtDNRbAIcQO/afXvu/VJ4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=x1YTEa+pYYZzpx6trqQHzjy6+vUTCftWGsHsHAqBFvv0tdY2BjBcueFR1FF5L2tjc 4rYKZWqUw757h6svsoknXcfwdPr+qkJMDicaxCI7FjeFpPA0SBS2aTLfiSWAOw3IcW jNwUbFQWWus0dXrFARu0/+ag7fB7iykJQEcxXCGg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728145AbgBTOBg (ORCPT ); Thu, 20 Feb 2020 09:01:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:40004 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727298AbgBTOBg (ORCPT ); Thu, 20 Feb 2020 09:01:36 -0500 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 9B11220722; Thu, 20 Feb 2020 14:01:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582207295; bh=PeA7JgpdUfYYu08f+gwb07KtDNRbAIcQO/afXvu/VJ4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=J2WQoS5XpWvVpW/EISmOiSkv/8LK6KNtcbTp6U8D8GyWJBA2ZMG0aAko5epk80vGu jYWo1/3CLzV32fdWpoy49UlpNlhad2EXZ7/pcrne6xx+AqNc5Zm5EvoYpmLjeUdMsG YgU6Zv8zoErOHPEJH6zIzdxBC0imCHec0oJq36aw= 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 1j4mOT-006k7A-Q9; Thu, 20 Feb 2020 14:01:34 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 20 Feb 2020 14:01:33 +0000 From: Marc Zyngier To: Robin Murphy Cc: Marek Szyprowski , Vladimir Murzin , Russell King , kvm@vger.kernel.org, Arnd Bergmann , Suzuki K Poulose , Quentin Perret , Christoffer Dall , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , James Morse , Julien Thierry , Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host In-Reply-To: References: <20200210141324.21090-1-maz@kernel.org> <621a0a92-6432-6c3e-cb69-0b601764fa69@samsung.com> <43446bd5e884ae92f243799cbe748871@kernel.org> Message-ID: <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.10 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: robin.murphy@arm.com, m.szyprowski@samsung.com, vladimir.murzin@arm.com, linux@arm.linux.org.uk, kvm@vger.kernel.org, arnd@arndb.de, suzuki.poulose@arm.com, qperret@google.com, Christoffer.Dall@arm.com, krzk@kernel.org, b.zolnierkie@samsung.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, pbonzini@redhat.com, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2020-02-20 13:32, Robin Murphy wrote: > On 20/02/2020 1:15 pm, Marc Zyngier wrote: >> Hi Marek, >> >> On 2020-02-20 12:44, Marek Szyprowski wrote: >>> Hi Marc, >>> >>> On 10.02.2020 15:13, 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 >>> >>> That is a bit sad information. Mainline Exynos finally got everything >>> that was needed to run it on the quite popular Samsung >>> Exynos5422-based >>> Odroid XU4/HC1/MC1 boards. According to the Odroid related forums it >>> is >>> being used. We also use it internally at Samsung. >> >> Something like "too little, too late" springs to mind, but let's be >> constructive. Is anyone using it in a production environment, where >> they rely on the latest mainline kernel having KVM support? >> >> The current proposal is to still have KVM support in 5.6, as well as >> ongoing support for stable kernels. If that's not enough, can you >> please >> explain your precise use case? > > Presumably there's no *technical* reason why the stable subset of v7 > support couldn't be stripped down and brought back private to arch/arm > if somebody really wants and is willing to step up and look after it? There is no technical reason at all, just a maintenance effort. The main killer is the whole MMU code, which I'm butchering with NV, and that I suspect Will will also turn upside down with his stuff. Not to mention the hypercall interface that will need a complete overhaul. If we wanted to decouple the two, we'd need to make the MMU code, the hypercalls, arm.c and a number of other bits private to 32bit. M. -- Jazz is not dead. It just smells funny...