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 9AD4EC11D05 for ; Thu, 20 Feb 2020 14:38:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 787CA20656 for ; Thu, 20 Feb 2020 14:38:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728042AbgBTOio (ORCPT ); Thu, 20 Feb 2020 09:38:44 -0500 Received: from foss.arm.com ([217.140.110.172]:44120 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727761AbgBTOio (ORCPT ); Thu, 20 Feb 2020 09:38:44 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AF19C31B; Thu, 20 Feb 2020 06:38:43 -0800 (PST) Received: from [10.1.196.37] (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 788F03F6CF; Thu, 20 Feb 2020 06:38:41 -0800 (PST) Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host To: Marc Zyngier 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 References: <20200210141324.21090-1-maz@kernel.org> <621a0a92-6432-6c3e-cb69-0b601764fa69@samsung.com> <43446bd5e884ae92f243799cbe748871@kernel.org> <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> From: Robin Murphy Message-ID: <5a984189-78bb-2707-3714-13edcee9e8f5@arm.com> Date: Thu, 20 Feb 2020 14:38:40 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 20/02/2020 2:01 pm, Marc Zyngier wrote: > 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. Right, the prospective kvm-arm maintainer's gameplan would essentially be an equivalent "move virt/kvm/arm to arch/arm/kvm" patch, but then ripping out all the Armv8 and GICv3 gubbins instead. Yes, there would then be lots of *similar* code to start with, but it would only diverge further as v8 architecture development continues independently. Anyway, I just thought it seemed worth saying out loud, to reassure folks that a realistic middle-ground between "yay bye!" and "oh no the end of the world!" does exist, namely "someone else's problem" :) Robin. 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 82377C11D0A for ; Thu, 20 Feb 2020 14:38:48 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 15C1A20656 for ; Thu, 20 Feb 2020 14:38:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 15C1A20656 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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 6C95E4AF38; Thu, 20 Feb 2020 09:38:47 -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 NGS710Rj2Imz; Thu, 20 Feb 2020 09:38:46 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4762E4AF3A; Thu, 20 Feb 2020 09:38:46 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 939B64AF38 for ; Thu, 20 Feb 2020 09:38:45 -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 Q5x95WH5qdvs for ; Thu, 20 Feb 2020 09:38:44 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 2C5864A968 for ; Thu, 20 Feb 2020 09:38:44 -0500 (EST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AF19C31B; Thu, 20 Feb 2020 06:38:43 -0800 (PST) Received: from [10.1.196.37] (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 788F03F6CF; Thu, 20 Feb 2020 06:38:41 -0800 (PST) Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host To: Marc Zyngier References: <20200210141324.21090-1-maz@kernel.org> <621a0a92-6432-6c3e-cb69-0b601764fa69@samsung.com> <43446bd5e884ae92f243799cbe748871@kernel.org> <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> From: Robin Murphy Message-ID: <5a984189-78bb-2707-3714-13edcee9e8f5@arm.com> Date: Thu, 20 Feb 2020 14:38:40 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> Content-Language: en-GB Cc: Russell King , kvm@vger.kernel.org, Arnd Bergmann , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , linux-arm-kernel@lists.infradead.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, Marek Szyprowski 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 On 20/02/2020 2:01 pm, Marc Zyngier wrote: > 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. Right, the prospective kvm-arm maintainer's gameplan would essentially be an equivalent "move virt/kvm/arm to arch/arm/kvm" patch, but then ripping out all the Armv8 and GICv3 gubbins instead. Yes, there would then be lots of *similar* code to start with, but it would only diverge further as v8 architecture development continues independently. Anyway, I just thought it seemed worth saying out loud, to reassure folks that a realistic middle-ground between "yay bye!" and "oh no the end of the world!" does exist, namely "someone else's problem" :) Robin. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 54CE2C11D0A for ; Thu, 20 Feb 2020 14:38:50 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 19E4B207FD for ; Thu, 20 Feb 2020 14:38:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="AcZwLHhf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19E4B207FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+37dqsqtQZnxBQ5kRr4pa9gubJnY9zIClW3OaZmlR0Y=; b=AcZwLHhfmfqc8z0yYMLoXcdmh PV+STKYPLYvK7vwDfWQzbMiqASydKzSVFV3ySdWpvw53AA8I31Hn604scCQnxq6efipQKMn+dm0rX BvW2OG3LqAEjAB0j1vnC+eBTBYefydxdb1knp862BUwVGPnFl69HYv14DiL7co5cfte8505Gyux0y m52vDpHBbRzzU5osAMhxAosZoFRMIMEAlW3VOTHxawPIFyAhdNT1lcjKHAtKSgJPsWxQAbKPKXkla lda0a5DVSJqc+OEn4O2IJXA24iBTTkB5qnQJXK5V2THR74a8LDuFILv5EJKRzSL00f5NjSWcTJijU Gx/IZydfw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4myW-00033i-Mi; Thu, 20 Feb 2020 14:38:48 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4myS-00032J-Up for linux-arm-kernel@lists.infradead.org; Thu, 20 Feb 2020 14:38:46 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AF19C31B; Thu, 20 Feb 2020 06:38:43 -0800 (PST) Received: from [10.1.196.37] (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 788F03F6CF; Thu, 20 Feb 2020 06:38:41 -0800 (PST) Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host To: Marc Zyngier References: <20200210141324.21090-1-maz@kernel.org> <621a0a92-6432-6c3e-cb69-0b601764fa69@samsung.com> <43446bd5e884ae92f243799cbe748871@kernel.org> <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> From: Robin Murphy Message-ID: <5a984189-78bb-2707-3714-13edcee9e8f5@arm.com> Date: Thu, 20 Feb 2020 14:38:40 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3f7f3b6c8b758b6d2134364616c6bc1e@kernel.org> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200220_063845_080497_0ACA881E X-CRM114-Status: GOOD ( 18.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Murzin , Russell King , kvm@vger.kernel.org, Arnd Bergmann , Suzuki K Poulose , Quentin Perret , Christoffer Dall , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , James Morse , linux-arm-kernel@lists.infradead.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry , Marek Szyprowski Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 20/02/2020 2:01 pm, Marc Zyngier wrote: > 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. Right, the prospective kvm-arm maintainer's gameplan would essentially be an equivalent "move virt/kvm/arm to arch/arm/kvm" patch, but then ripping out all the Armv8 and GICv3 gubbins instead. Yes, there would then be lots of *similar* code to start with, but it would only diverge further as v8 architecture development continues independently. Anyway, I just thought it seemed worth saying out loud, to reassure folks that a realistic middle-ground between "yay bye!" and "oh no the end of the world!" does exist, namely "someone else's problem" :) Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel