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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DB768C87FCB for ; Fri, 8 Aug 2025 04:06:28 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ukEMO-0004Mh-GZ; Fri, 08 Aug 2025 00:05:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ukEM5-0003mB-01 for qemu-devel@nongnu.org; Fri, 08 Aug 2025 00:05:22 -0400 Received: from mgamail.intel.com ([198.175.65.11]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ukEM2-0000Pn-CX for qemu-devel@nongnu.org; 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07 Aug 2025 21:05:00 -0700 X-CSE-ConnectionGUID: wR1rMv0NR4yQnUNVA7A1PA== X-CSE-MsgGUID: g8dKih5DSai902xvvj7JGA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.17,274,1747724400"; d="scan'208";a="169352137" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.247.1]) ([10.124.247.1]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Aug 2025 21:04:57 -0700 Message-ID: <09cf398f-9469-4778-a458-3a2a87fb7a60@intel.com> Date: Fri, 8 Aug 2025 12:04:54 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: split lock issue in multiboot_dma.bin From: Xiaoyao Li To: =?UTF-8?Q?Marcus_H=C3=A4hnel?= , Adam Lackorzynski , Paolo Bonzini Cc: "qemu-devel@nongnu.org" , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Chenyi Qiang References: <0344ef5a-8c6c-4c21-824e-9506bb4c7600@intel.com> Content-Language: en-US In-Reply-To: <0344ef5a-8c6c-4c21-824e-9506bb4c7600@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=198.175.65.11; envelope-from=xiaoyao.li@intel.com; helo=mgamail.intel.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HK_RANDOM_ENVFROM=0.001, HK_RANDOM_FROM=0.001, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 8/8/2025 12:00 AM, Xiaoyao Li wrote: > On 8/7/2025 8:15 PM, Xiaoyao Li wrote: >> When running the kvm-unit-tests on Intel platforms with "split lock >> disable" feature, every test triggers a kernel warning of >> >>      x86/split lock detection: #AC: qemu-system-x86_64/373232 took a >> split_lock trap at address: 0x1e3 >> >> After investigation, it turns out the split lock happens from >> multiboot_dma.bin: >> >> Hack KVM by exiting to QEMU on split lock #AC, we get >> >> KVM: exception 17 exit (error code 0x0) >> EAX=00000001 EBX=00000000 ECX=00000014 EDX=0001fb80 >> ESI=00000000 EDI=000000a8 EBP=00000000 ESP=00006f10 >> EIP=000001e3 EFL=00010002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0 >> ES =0900 00009000 0000ffff 00009300 DPL=0 DS16 [-WA] >> CS =c000 000c0000 0000ffff 00009b00 DPL=0 CS16 [-RA] >> SS =0000 00000000 0000ffff 00009300 DPL=0 DS16 [-WA] >> DS =c000 000c0000 0000ffff 00009300 DPL=0 DS16 [-WA] >> FS =0950 00009500 0000ffff 00009300 DPL=0 DS16 [-WA] >> GS =06f2 00006f20 0000ffff 00009300 DPL=0 DS16 [-WA] >> LDT=0000 00000000 0000ffff 00008200 DPL=0 LDT >> TR =0000 00000000 0000ffff 00008b00 DPL=0 TSS32-busy >> GDT=     000c02b4 00000027 >> IDT=     00000000 000003ff >> CR0=00000011 CR2=00000000 CR3=00000000 CR4=00000000 >> DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 >> DR3=0000000000000000 >> DR6=00000000ffff0ff0 DR7=0000000000000400 >> EFER=0000000000000000 >> Code=89 16 08 00 65 66 0f 01 16 06 00 66 b8 01 00 00 00 0f 22 c0 <65> >> 66 ff 2e 00 00 b8 10 00 00 00 8e d0 8e d8 8e c0 8e e0 8e e8 66 b8 08 >> 00 66 ba 10 05 66 >> >> And it matches with what disassembled from multiboo_dma.bin: >> >> #objdump -b binary -m i386 -D pc-bios/multiboot_dma.bin >> >>   1d1:   08 00                   or     %al,(%eax) >>   1d3:   65 66 0f 01 16          lgdtw  %gs:(%esi) >>   1d8:   06                      push   %es >>   1d9:   00 66 b8                add    %ah,-0x48(%esi) >>   1dc:   01 00                   add    %eax,(%eax) >>   1de:   00 00                   add    %al,(%eax) >>   1e0:   0f 22 c0                mov    %eax,%cr0 >>  >1e3:   65 66 ff 2e             ljmpw  *%gs:(%esi) >>   1e7:   00 00                   add    %al,(%eax) >>   1e9:   b8 10 00 00 00          mov    $0x10,%eax >>   1ee:   8e d0                   mov    %eax,%ss >>   1f0:   8e d8                   mov    %eax,%ds >>   1f2:   8e c0                   mov    %eax,%es >>   1f4:   8e e0                   mov    %eax,%fs >>   1f6:   8e e8                   mov    %eax,%gs >>   1f8:   66 b8 08 00             mov    $0x8,%ax >>   1fc:   66 ba 10 05             mov    $0x510,%dx >> >> I don't know where the multiboot_dma.bin are built from so that I >> cannot further help resolve the split lock issue. > > stupid me. The src code is just pc-bios/optionrom/multiboot.S > But I don't know how to build a bin file from it to test my fix. I resolve it myself. It turns out my machine lacks some crosscc package. QEMU can build optionroms after I install g++-multilib． I then verified my fix and sent it: https://lore.kernel.org/qemu-devel/20250808035027.2194673-1-xiaoyao.li@intel.com/