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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 E0A36C11D04 for ; Thu, 20 Feb 2020 10:29:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B4DBC24656 for ; Thu, 20 Feb 2020 10:29:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582194555; bh=89ixU0szikhKLR+8AWYd9tNddCd483x7QZqiB73/Uco=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=SrYgYMhAV6J+3DIR7P0pabZ/N9lN2aWAUjQTwc508lmJA0Bb0OGxqTR1KTzJjXl84 /sL12CqY9utDTasYpfucr8cbuqM09JgBqGwgYqPjssqWFl/t6UWRbih4jsRlzizdcF ih/7Pl8RSjgOvRPyCsvkKIVcgkt1E3ETnlFyYPyQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727589AbgBTK3O (ORCPT ); Thu, 20 Feb 2020 05:29:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:39206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726801AbgBTK3O (ORCPT ); Thu, 20 Feb 2020 05:29:14 -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 5BF7C20801; Thu, 20 Feb 2020 10:29:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582194553; bh=89ixU0szikhKLR+8AWYd9tNddCd483x7QZqiB73/Uco=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=JeR9EVZCzgexZ6fjQV7E14xQO/TIF++cY0/wAZwh8aOBHdJe2DzMtcZYuoHsMi+k6 YY+hiAp/34k9+IefUfaLKdW9OLyr4CTj//t7rwxabjvF/OwgtM99osg+kVoFeOpptK pUiaBngxgCh1evcY65CNc81K5XeY09g0f7hp8waw= 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 1j4j4x-006hip-NY; Thu, 20 Feb 2020 10:29:11 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 20 Feb 2020 10:29:11 +0000 From: Marc Zyngier To: Jan Kiszka Cc: Arnd Bergmann , Linux ARM , kvmarm@lists.cs.columbia.edu, kvm list , James Morse , Julien Thierry , Suzuki K Poulose , Paolo Bonzini , Christoffer Dall , Will Deacon , Quentin Perret , Russell King , Vladimir Murzin , Anders Berg , jailhouse-dev@googlegroups.com, jean-philippe.brucker@arm.com Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host In-Reply-To: References: <20200210141324.21090-1-maz@kernel.org> Message-ID: <535d8a4498d81b4901dfab232638d865@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: jan.kiszka@siemens.com, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, pbonzini@redhat.com, Christoffer.Dall@arm.com, will@kernel.org, qperret@google.com, linux@arm.linux.org.uk, vladimir.murzin@arm.com, anders.berg@lsi.com, jailhouse-dev@googlegroups.com, jean-philippe.brucker@arm.com 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 2020-02-19 15:46, Jan Kiszka wrote: > On 19.02.20 16:09, Arnd Bergmann wrote: >> On Mon, Feb 10, 2020 at 3:13 PM 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. >>> >>> To reiterate: 32bit guest support for arm64 stays, of course. Only >>> 32bit host goes. Once this is merged, I plan to move virt/kvm/arm to >>> arm64, and cleanup all the now unnecessary abstractions. >>> >>> The patches have been generated with the -D option to avoid spamming >>> everyone with huge diffs, and there is a kvm-arm/goodbye branch in >>> my kernel.org repository. >> >> Just one more thought before it's gone: is there any shared code >> (header files?) that is used by the jailhouse hypervisor? >> >> If there is, are there any plans to merge that into the mainline >> kernel >> for arm32 in the near future? >> >> I'm guessing the answer to at least one of those questions is 'no', so >> we don't need to worry about it, but it seems better to ask. > > Good that you mention it: There is one thing we share on ARM (and > ARM64), and that is the hypervisor enabling stub, to install our own > vectors. If that was to be removed as well, we would have to patch it > back downstream. So far, we only carry few EXPORT_SYMBOL patches for > essential enabling. I actually have a few extra patches on top of the series, one of them actually removing the ability to register new vectors (mostly because I don't like leaving unused stuff behind), see [1]. I'll post an update so that we can discuss whether we want this particular to stay or not. > That said, I was also starting to think about how long we will > continue to support Jailhouse on 32-bit ARM. We currently have no > supported SoC there that comes with an SMMU, and I doubt to see one > still showing up. So, Jailhouse on ARM is really just a testing/demo > case, maybe useful (but I didn't get concrete feedback) for cleaner > collaborative AMP for real-time purposes, without security concerns. I > assume 32-bit ARM will never be part of what would be proposed of > Jailhouse for upstream. I guess we all come to the same conclusion... M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm/goodbye&id=0943dd119105b65197adffda52c402cce28da56d -- Jazz is not dead. It just smells funny...