From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752759AbcHMPRY (ORCPT ); Sat, 13 Aug 2016 11:17:24 -0400 Received: from mail-bn3nam01on0053.outbound.protection.outlook.com ([104.47.33.53]:42653 "EHLO NAM01-BN3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752398AbcHMPRU (ORCPT ); Sat, 13 Aug 2016 11:17:20 -0400 X-Greylist: delayed 559 seconds by postgrey-1.27 at vger.kernel.org; Sat, 13 Aug 2016 11:17:19 EDT Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Yuri.Norov@caviumnetworks.com; Date: Sat, 13 Aug 2016 18:17:03 +0300 From: Yury Norov To: Catalin Marinas CC: Arnd Bergmann , , , , Hanjun Guo , , , , , , Andrew Pinski , , , , , , , , "Zhangjian (Bamvor)" , Bamvor Jian Zhang , , , , , , Andrew Pinski , , , Subject: Re: [PATCH 05/19] arm64: rename COMPAT to AARCH32_EL0 in Kconfig Message-ID: <20160813151703.GC24335@yury-N73SV> References: <1466207668-10549-1-git-send-email-ynorov@caviumnetworks.com> <6457502.FRufylo3sd@wuerfel> <20160811163003.GD18366@e104818-lin.cambridge.arm.com> <2034620.lN3lAEBAXs@wuerfel> <20160812143612.GH12939@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; 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OTOH, people are > > > > > abusing this and write 32-bit apps relying on the 64-bit /proc/cpuinfo: > > > > > > > > > > http://lkml.kernel.org/g/1464706504-25224-3-git-send-email-catalin.marinas@arm.com > > > > > > > > > > (you were summoned on that discussion couple of times ;)) > > > > > > > > Hmm, I thought I saw the thread and didn't have any good idea for > > > > the uname information, but didn't notice it was for /proc/cpuinfo. > > > > > > > > What's wrong with always showing both the 32-bit and the 64-bit > > > > hwcap strings here (minus the duplicates, which hopefully have > > > > the same meaning here)? > > > > > > As I said above, some of them have the same name (which may be a good > > > thing at a first look) but we don't have an architecture guarantee that > > > the feature is present in both AArch32 and AArch64 modes (e.g. AES may > > > only be available in AArch64). > > > > Is this the case on actual implementations that exist today? If they > > are actually always both present, we might be able to get away with it. > > It may be fine on current implementations but what would we do when/if > we actually find such discrepancy? It's not just ARM Ltd designing the > chips, so as long as the architecture doesn't mandate it you may find > strange implementations. > > Imposing such restriction in the architecture doesn't make sense if the > only reason is the /proc/cpuinfo file (and I can't think of any other > reason why this should be enforced). > > What I'm worried about is 32-bit apps running on an arm64 kernel and > making use of the 64-bit /proc/cpuinfo without any guarantee that the > AArch32 state has such features. In my patch proposal linked above I > wanted to always force the compat /proc/cpuinfo for 32-bit tasks. The link doesn't work for me. Is there other link, or what's the maillist there? So, what we decided finally? Is my understanding correct that we leave everything as is in ilp32 series, and it will be resolved separately? Yury. > > -- > Catalin