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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 1F6F7C25B08 for ; Wed, 17 Aug 2022 10:52:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3ZTmZbhb5nu3mFj3ipM6l39NTEUCLagleb/O6ir9Umc=; b=w2hgEsegtnh92A cQStHRoqwhVb8/3AgK+wRgN9VDavQGAule5x/zOzx8hbgOXqGM8AOJu5gOnqi8sxfgwGm2l8NHPl+ ySu4uLnBM5lxVRcs6EUdw/OlhORkhYEHxmBiHhCxKvJcpd6M5ujvA+KIhGcCfa9Kryhmvs7KimRrX uW1Tpp7HXoYPYl5ME25T5RIj7d102q6O3j1J/mZGIdKzWSv5OvPM1SNZTk30AWZH5CQNhfqu4B3GG Zp8ZxzqYgSu7DeaZlKr0QNesZGc6xzpR8jaR5Pz6wZS1P3HtFCbpJk3MdJYzmET6np7X3iXwqCZp8 5ozIMZ0oegFt9APZAZhQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oOGeE-000tLL-Jo; Wed, 17 Aug 2022 10:51:42 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oOGeA-000tG3-32 for linux-arm-kernel@lists.infradead.org; Wed, 17 Aug 2022 10:51:39 +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 5241C113E; Wed, 17 Aug 2022 03:51:29 -0700 (PDT) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1FCB13F67D; Wed, 17 Aug 2022 03:51:26 -0700 (PDT) Date: Wed, 17 Aug 2022 11:52:06 +0100 From: Alexandru Elisei To: Marc Zyngier 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 Message-ID: References: <20220816192554.1455559-1-oliver.upton@linux.dev> <87tu6bw5dd.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87tu6bw5dd.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220817_035138_254109_0E6D082B X-CRM114-Status: GOOD ( 21.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. Thanks, Alex > > Anyway, I've applied this to fixes. > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel