From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: x86: Corrupted eflags in qemu's CPU state Date: Mon, 26 Jan 2009 16:49:59 +0100 Message-ID: <497DDBA7.1040103@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit To: kvm-devel Return-path: Received: from gecko.sbs.de ([194.138.37.40]:16779 "EHLO gecko.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332AbZAZPt7 (ORCPT ); Mon, 26 Jan 2009 10:49:59 -0500 Received: from mail1.sbs.de (localhost [127.0.0.1]) by gecko.sbs.de (8.12.11.20060308/8.12.11) with ESMTP id n0QFnuP2013419 for ; Mon, 26 Jan 2009 16:49:56 +0100 Received: from [139.25.109.167] (mchn012c.mchp.siemens.de [139.25.109.167] (may be forged)) by mail1.sbs.de (8.12.11.20060308/8.12.11) with ESMTP id n0QFnuIv008721 for ; Mon, 26 Jan 2009 16:49:56 +0100 Sender: kvm-owner@vger.kernel.org List-ID: Hi, this line almost ruined my afternoon: diff --git a/qemu/qemu-kvm-x86.c b/qemu/qemu-kvm-x86.c index 01748ed..4ad386b 100644 --- a/qemu/qemu-kvm-x86.c +++ b/qemu/qemu-kvm-x86.c @@ -429,7 +429,6 @@ void kvm_arch_save_regs(CPUState *env) env->cc_src = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C); env->df = 1 - (2 * ((env->eflags >> 10) & 1)); env->cc_op = CC_OP_EFLAGS; - env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C); /* msrs */ n = 0; The guest flags reported via gdb or monitor were garbage and I first didn't realized this... git logs revealed that commit 6eecdc3eea74ead3c11b8b43d825d2cabe7a2456 once introduced it mid of 2006, but maybe under different boundary conditions. At least today it appears to be plain wrong, eflags must always contain to full state, cc_src, df & cc_op are just supplementary states. Please correct me if I'm wrong, otherwise I will send out a proper patch, also upstream as QEMU's kvm suffers from the same issue. Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux