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=-4.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 1BF1CC433C1 for ; Sun, 28 Mar 2021 12:38:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB8D361964 for ; Sun, 28 Mar 2021 12:38:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230223AbhC1MiD (ORCPT ); Sun, 28 Mar 2021 08:38:03 -0400 Received: from mx-out.tlen.pl ([193.222.135.175]:26369 "EHLO mx-out.tlen.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229757AbhC1Mh7 (ORCPT ); Sun, 28 Mar 2021 08:37:59 -0400 Received: (wp-smtpd smtp.tlen.pl 22659 invoked from network); 28 Mar 2021 14:37:56 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=o2.pl; s=1024a; t=1616935076; bh=7Svvik2UzcKhTxyxI6ZgB3tQFlLo0yPD+EfYuon8cLY=; h=To:Cc:From:Subject; b=srqXskzkMQ2npBRklBgqc42lXY3/vUxigFLXhqzylS2C8A23Jg7ApZp9cfDjOALIf VoPATjIysOgFLtCIgG489sgnbwAinOxM7521n5IQD566OmCG3iwKnHoXyonJow4I+4 snJ9Y/jdSnQKBUWhBfEoA/2wO5jRhjcpM89kGdM8= Received: from aclp172.neoplus.adsl.tpnet.pl (HELO [192.168.1.22]) (mat.jonczyk@o2.pl@[83.10.117.172]) (envelope-sender ) by smtp.tlen.pl (WP-SMTPD) with ECDHE-RSA-AES256-GCM-SHA384 encrypted SMTP for ; 28 Mar 2021 14:37:56 +0200 Message-ID: <059b4775-e130-27c4-26fc-3a0eca07ddae@o2.pl> Date: Sun, 28 Mar 2021 14:37:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Thunderbird/87.0 Content-Language: en-GB To: Thomas Gleixner , Willy Tarreau Cc: linux-kernel@vger.kernel.org References: <20210327203218.119372-1-mat.jonczyk@o2.pl> <20210327211322.121708-1-mat.jonczyk@o2.pl> <20210327232551.GA20783@1wt.eu> <87lfa8cchf.ffs@nanos.tec.linutronix.de> From: =?UTF-8?Q?Mateusz_Jo=c5=84czyk?= Subject: Re: Testers wanted: Atom netbooks with x86_64 disabled by BIOS In-Reply-To: <87lfa8cchf.ffs@nanos.tec.linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-WP-MailID: 354c18b07433a45bda22440b695f33a7 X-WP-AV: skaner antywirusowy Poczty o2 X-WP-SPAM: NO 0000000 [EbOU] Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org W dniu 28.03.2021 o 00:25, Willy Tarreau pisze: > FWIW I tested on my ASUS 1025C which runs on an Atom N2600 forced to > 32-bit. I had already tried in the past but wanted to give it a try > again in case I'd have missed anything. Sadly it didn't work, I'm > still getting the "requires an x86-64 CPU" message. Thank you. It looks like your bootloader uses the 16-bit kernel boot protocol. The 16-bit kernel boot code checks for x86_64 presence with a similar message ( inside arch/x86/boot/cpu.c ), which I did not patch out. If you would like to test again, use the same patched kernel, but change in GRUB: "linux16" to "linux" and "initrd16" to "initrd" to use the 32-bit boot protocol. Which distribution and bootloader do you use? W dniu 28.03.2021 o 03:07, Thomas Gleixner pisze: > There are some of these '32bit only' CPUs out there in the wild which > actually support long mode. Some of them even do not have the long mode > CPUID bit fused out. But whether it works is a different story: > >   - If the CPUID bit is on, then the chance is high, but it runs out of >     spec (guarantee wise) > >   - If it's off is still might work by some definition of work as they >     might have fused off more or there are actual defects in some 64bit >     only area which are irrelevant when in 32bit mode. Of course, force enabling x86_64 would require passing a kernel command line parameter with a prominent warning in documentation, just like with "forcepae". Greetings, Mateusz