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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 DE5E6C63777 for ; Sat, 21 Nov 2020 07:36:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A03522264 for ; Sat, 21 Nov 2020 07:36:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="NBoERCzx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727118AbgKUHfq (ORCPT ); Sat, 21 Nov 2020 02:35:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:57236 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726161AbgKUHfp (ORCPT ); Sat, 21 Nov 2020 02:35:45 -0500 Received: from mail-oi1-f177.google.com (mail-oi1-f177.google.com [209.85.167.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A43012224A; Sat, 21 Nov 2020 07:35:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605944144; bh=JIOyIP3Z1qYK7PEjNX1ygOHQ10RRXlMdlRpxuOVqaF4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=NBoERCzx0bOfs1Spi/qI4Jr4R9gR8nafDvLzNl5y954yhL+AaVOlArn46YJkANI7T 7abJYj5XFHRgl30rA/lbg/rqlMovYayapPUq/NdCriwpLmDqbHGPoFB/SLz/cLTFne 1lltJvXcAoTRU2aCkyn4SJsnZCZs0Biim543HgXo= Received: by mail-oi1-f177.google.com with SMTP id c80so13347823oib.2; Fri, 20 Nov 2020 23:35:44 -0800 (PST) X-Gm-Message-State: AOAM533XGJRslAI2T+3QpkpO+RvNRSTokXUTYapch7qFcAvRgtNw5gjL pF3r1REgFKT6pLRKz68m5wAup7lQ0Now8fP87ps= X-Google-Smtp-Source: ABdhPJx40jOdwbcNKyqzBINwkmCmwPpkhWi97MwgNpvEdbPfdyMgPT4NA53Xt6JomdsOtV9RsBYuyUMJZVUA9Le699M= X-Received: by 2002:aca:d4d5:: with SMTP id l204mr7701517oig.174.1605944144026; Fri, 20 Nov 2020 23:35:44 -0800 (PST) MIME-Version: 1.0 References: <20201118220731.925424-1-samitolvanen@google.com> In-Reply-To: From: Ard Biesheuvel Date: Sat, 21 Nov 2020 08:35:33 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v7 00/17] Add support for Clang LTO To: Nick Desaulniers Cc: Sami Tolvanen , Masahiro Yamada , Steven Rostedt , Will Deacon , Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , PCI , Alistair Delva Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 21 Nov 2020 at 00:53, Nick Desaulniers wrote: > > On Fri, Nov 20, 2020 at 3:30 PM Ard Biesheuvel wrote: > > > > On Fri, 20 Nov 2020 at 21:19, Nick Desaulniers wrote: > > > > > > On Fri, Nov 20, 2020 at 2:30 AM Ard Biesheuvel wrote: > > > > > > > > On Thu, 19 Nov 2020 at 00:42, Nick Desaulniers wrote: > > > > > > > > > > Thanks for continuing to drive this series Sami. For the series, > > > > > > > > > > Tested-by: Nick Desaulniers > > > > > > > > > > I did virtualized boot tests with the series applied to aarch64 > > > > > defconfig without CONFIG_LTO, with CONFIG_LTO_CLANG, and a third time > > > > > with CONFIG_THINLTO. If you make changes to the series in follow ups, > > > > > please drop my tested by tag from the modified patches and I'll help > > > > > re-test. Some minor feedback on the Kconfig change, but I'll post it > > > > > off of that patch. > > > > > > > > > > > > > When you say 'virtualized" do you mean QEMU on x86? Or actual > > > > virtualization on an AArch64 KVM host? > > > > > > aarch64 guest on x86_64 host. If you have additional configurations > > > that are important to you, additional testing help would be > > > appreciated. > > > > > > > Could you run this on an actual phone? Or does Android already ship > > with this stuff? > > By `this`, if you mean "the LTO series", it has been shipping on > Android phones for years now, I think it's even required in the latest > release. > > If you mean "the LTO series + mainline" on a phone, well there's the > android-mainline of https://android.googlesource.com/kernel/common/, > in which this series was recently removed in order to facilitate > rebasing Android's patches on ToT-mainline until getting the series > landed upstream. Bit of a chicken and the egg problem there. > > If you mean "the LTO series + mainline + KVM" on a phone; I don't know > the precise state of aarch64 KVM and Android (Will or Marc would > know). We did experiment recently with RockPI's for aach64 KVM, IIRC; > I think Android is tricky as it still requires A64+A32/T32 chipsets, > Alistair would know more. Might be interesting to boot a virtualized > (or paravirtualized?) guest built with LTO in a host built with LTO > for sure, but I don't know if we have tried that yet (I think we did > try LTO guests of android kernels, but I think they were on the stock > RockPI host BSP image IIRC). > I don't think testing under KVM gives us more confidence or coverage than testing on bare metal. I was just pointing out that 'virtualized' is misleading, and if you test things under QEMU/x86 + TCG, it is better to be clear about this, and refer to it as 'under emulation'.