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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12E30C32772 for ; Wed, 17 Aug 2022 10:57:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238810AbiHQK47 (ORCPT ); Wed, 17 Aug 2022 06:56:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52634 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239028AbiHQK46 (ORCPT ); Wed, 17 Aug 2022 06:56:58 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED24F647E8 for ; Wed, 17 Aug 2022 03:56:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id CF8DBCE1C60 for ; Wed, 17 Aug 2022 10:56:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7F17C433D6; Wed, 17 Aug 2022 10:56:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660733812; bh=ZNdNzMIFxsFYE2eCeNZAdKQ9jf8HnxCpnG6eMatEQsI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=T//1zIjCmYwOk7lXGUJtuGwr4JkGDbc4QFdSoJSpEZ92MkOmwNqoaE74JFFai+R4e c8gzAXxiVxfJOIYBBMge0HoAk26wM0aNdyyIsGGy1t3fRKdWWFxzmEdGrmysZbV1su BzrFL8PE5vEJAzCIM4UgXAyQrVCgqlh79jWXTZ4lcq95y8Q7TkJSFyG7UZ6tr/Te3b h38khwY94b9lyFYT2Rw9M2ywuq+4lnlY0UG31o+RDuGZockELuMA1bjXOUaFbLjgL8 +TDBFninuVVe3jqZsmYg/nLGQaGoFledsszsEuL6CX0El6dE9vQYHOPRPZPRKRJuQf j05VfPTvitkmA== Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1oOGjC-003iDB-OR; Wed, 17 Aug 2022 11:56:50 +0100 Date: Wed, 17 Aug 2022 11:56:50 +0100 Message-ID: <87sflvw32l.wl-maz@kernel.org> From: Marc Zyngier To: Alexandru Elisei Cc: Oliver Upton , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, will@kernel.org Subject: Re: [PATCH v2 0/2] KVM: arm64: Uphold 64bit-only behavior on asymmetric systems In-Reply-To: References: <20220816192554.1455559-1-oliver.upton@linux.dev> <87tu6bw5dd.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: alexandru.elisei@arm.com, oliver.upton@linux.dev, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, 17 Aug 2022 11:52:06 +0100, Alexandru Elisei wrote: > > Hi, > > On Wed, Aug 17, 2022 at 11:07:10AM +0100, Marc Zyngier wrote: > > On Tue, 16 Aug 2022 20:25:52 +0100, > > Oliver Upton wrote: > > > > > > Small series to fix a couple issues around when 64bit-only behavior is > > > applied. As KVM is more restrictive than the kernel in terms of 32bit > > > support (no asymmetry), we really needed our own predicate when the > > > meaning of system_supports_32bit_el0() changed in commit 2122a833316f > > > ("arm64: Allow mismatched 32-bit EL0 support"). > > > > > > Lightly tested as I do not have any asymmetric systems on hand at the > > > moment. Attention on patch 2 would be appreciated as it affects ABI. > > > > I don't think this significantly affect the ABI, as it is pretty > > unlikely that you'd have been able to execute the result, at least on > > VM creation (set PSTATE.M=USR, start executing, get the page fault on > > the first instruction... bang). > > > > You could have tricked it in other ways, but at the end of the day > > you're running a broken hypervisor on an even more broken system... > > Just FYI, you can create such a system on models, by running two clusters > and setting clusterX.max_32bit_el=-1. Or you can have even crazier > configurations, where AArch32 support is present on only one cluster, and > only for EL0. You mean, just as crazy as some of the systems out there? :D Thanks, M. -- Without deviation from the norm, progress is not possible.