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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 6C598C433C1 for ; Sat, 27 Mar 2021 20:40:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BE7361969 for ; Sat, 27 Mar 2021 20:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230259AbhC0UkA (ORCPT ); Sat, 27 Mar 2021 16:40:00 -0400 Received: from mx-out.tlen.pl ([193.222.135.145]:59884 "EHLO mx-out.tlen.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230002AbhC0Ujp (ORCPT ); Sat, 27 Mar 2021 16:39:45 -0400 X-Greylist: delayed 396 seconds by postgrey-1.27 at vger.kernel.org; Sat, 27 Mar 2021 16:39:45 EDT Received: (wp-smtpd smtp.tlen.pl 4720 invoked from network); 27 Mar 2021 21:33:03 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=o2.pl; s=1024a; t=1616877184; bh=JuabIowwXjMlE1i/TVQ4jxLohpJBzzcBMU6nptsqkFo=; h=From:To:Cc:Subject; b=EXIWs+Q80PxXhQyGfJFZQsLp+Q5aidrONoqtDorKudjRNEN3mdKAzKHnfXkhlH/r6 nbLgSdWMlThdiGg/mfh6qq5vU1DMc2UCxHRr+xo6qapccS1UxXHKzy2l/ZHVq4Uq+e crbGCwZjiruaz0jcMWSNbNz8oNPTV8Ar0Z+ZJFwI= Received: from aclp172.neoplus.adsl.tpnet.pl (HELO localhost.localdomain) (mat.jonczyk@o2.pl@[83.10.117.172]) (envelope-sender ) by smtp.tlen.pl (WP-SMTPD) with SMTP for ; 27 Mar 2021 21:33:03 +0100 From: =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org Subject: Testers wanted: Atom netbooks with x86_64 disabled by BIOS Date: Sat, 27 Mar 2021 21:32:18 +0100 Message-Id: <20210327203218.119372-1-mat.jonczyk@o2.pl> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-WP-MailID: c87522c42fe7c5357912513f254d7fc5 X-WP-AV: skaner antywirusowy Poczty o2 X-WP-SPAM: NO 0000000 [gQPk] Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, There are some netbooks with Intel Atom processors that have 64-bit support disabled by BIOS. Theoretically, the processor supports 64-bit operation, but BIOS allows only 32-bit code to run. I wonder whether the 64-bit mode is really disabled in the CPU or only hidden in the CPUID flags. If the latter, the computer could be made to run a 64-bit kernel. Similarly, there are some Pentium M processors that support PAE (Physical Address Extensions), but do not show this in CPUID. They could be made to run distributions that require PAE with the "forcepae" kernel command line parameter. I would like to ask people with such netbooks to try to run a 64-bit kernel with this patch applied. When a patched 64-bit kernel is run in `qemu-system-i386`, the virtual machine restarts instantly. Without this patch in such a case a 64-bit kernel hangs indefinitely (inside .Lno_longmode in head_64.S). CC: Thomas Gleixner CC: Ingo Molnar CC: Borislav Petkov CC: Signed-off-by: Mateusz Jończyk --- arch/x86/boot/compressed/head_64.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index e94874f4bbc1..23c376d0b221 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -112,7 +112,7 @@ SYM_FUNC_START(startup_32) call verify_cpu testl %eax, %eax - jnz .Lno_longmode + #jnz .Lno_longmode /* * Compute the delta between where we were compiled to run at -- 2.25.1