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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B74E9C433ED for ; Thu, 22 Apr 2021 11:04:45 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 0B221613C2 for ; Thu, 22 Apr 2021 11:04:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B221613C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bugs.launchpad.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51850 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZX8V-0000Pl-TQ for qemu-devel@archiver.kernel.org; Thu, 22 Apr 2021 07:04:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60564) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZWvG-0001iv-21 for qemu-devel@nongnu.org; Thu, 22 Apr 2021 06:51:02 -0400 Received: from indium.canonical.com ([91.189.90.7]:34826) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lZWvD-0006vf-NW for qemu-devel@nongnu.org; Thu, 22 Apr 2021 06:51:01 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1lZWvA-0005sU-IZ for ; Thu, 22 Apr 2021 10:50:56 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 79C4F2E816C for ; Thu, 22 Apr 2021 10:50:56 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 22 Apr 2021 10:41:43 -0000 From: Alexander Richardson <1916269@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: arichardson X-Launchpad-Bug-Reporter: Alexander Richardson (arichardson) X-Launchpad-Bug-Modifier: Alexander Richardson (arichardson) References: <161375459275.29060.15778429539023668893.malonedeb@soybean.canonical.com> Message-Id: <161908810382.6637.2396062733185532941.malone@chaenomeles.canonical.com> Subject: [Bug 1916269] Re: TCG: QEMU raises exception on SSE4.2 CRC32 instruction in kernel X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="1552fceb1603b3da6cfa437575d9c9fc4b2e683a"; Instance="production" X-Launchpad-Hash: b6d5bd93058a071eecd9cae2bf49c133da008e10 Received-SPF: none client-ip=91.189.90.7; envelope-from=bounces@canonical.com; helo=indium.canonical.com X-Spam_score_int: -65 X-Spam_score: -6.6 X-Spam_bar: ------ X-Spam_report: (-6.6 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1916269 <1916269@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Could someone familiar with the target/i386 decode logic could have a look = at this? It should be a rather simple change to avoid the exception for the= crc32 encoding. However, I am not familiar with x86 instruction encodings = so it would take me a long time to come up with a correct patch. Thanks! ** Summary changed: - TCG: QEMU raises exception on SSE4.2 CRC32 instruction in kernel + TCG: QEMU incorrectly raises exception on SSE4.2 CRC32 instruction -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1916269 Title: TCG: QEMU incorrectly raises exception on SSE4.2 CRC32 instruction Status in QEMU: New Bug description: If I run FreeBSD on QEMU 5.2 with TCG acceleration -cpu Nehalem, I get a FPU exception when executing crc32 (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D253617). This is not a problem with the default CPU (or KVM) since that does not support SSE 4.2. Attaching GDB shows this is triggered in target/i386/tcg/translate.c:3067 /* simple MMX/SSE operation */ if (s->flags & HF_TS_MASK) { gen_exception(s, EXCP07_PREX, pc_start - s->cs_base); return; } However, according to https://software.intel.com/sites/default/files/m/8/b/8/D9156103.pdf, page 61 the CRC32 instruction works no matter what the value of the TS bit. The code sequence in question is: 0xffffffff8105a4de <+126>: f2 48 0f 38 f1 de crc32q %rsi,%rbx 0xffffffff8105a4e4 <+132>: f2 48 0f 38 f1 ca crc32q %rdx,%rcx. This should work even with the FPU disabled. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1916269/+subscriptions