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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53CB2C32772 for ; Wed, 17 Aug 2022 10:51:33 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B94514D0BC; Wed, 17 Aug 2022 06:51:32 -0400 (EDT) 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 cnOd8MLnEmBg; Wed, 17 Aug 2022 06:51:31 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8723D4D136; Wed, 17 Aug 2022 06:51:31 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8F3A34D00F for ; Wed, 17 Aug 2022 06:51:30 -0400 (EDT) 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 QoI3QeCDZv2J for ; Wed, 17 Aug 2022 06:51:29 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 11F6F4D0BC for ; Wed, 17 Aug 2022 06:51:29 -0400 (EDT) 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 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> Cc: kvm@vger.kernel.org, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm