From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38746) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIgZB-0002KF-Pv for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:34:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIgYt-0005SS-RK for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:34:00 -0400 Received: from gmplib-02.nada.kth.se ([130.237.222.242]:50530 helo=shell.gmplib.org) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIgYt-0005Pj-J4 for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:33:47 -0400 References: <20130317193406.10807.11580.malonedeb@wampee.canonical.com> <20130317193406.10807.11580.malonedeb@wampee.canonical.com> <5148ABBC.2090507@twiddle.net> From: Torbjorn Granlund Sender: tg@gmplib.org Date: Thu, 21 Mar 2013 15:33:36 +0100 In-Reply-To: <5148ABBC.2090507@twiddle.net> (Richard Henderson's message of "Tue\, 19 Mar 2013 11\:17\:32 -0700") Message-ID: <86r4j8960v.fsf@shell.gmplib.org> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-=" Subject: Re: [Qemu-devel] [Bug 1156313] [NEW] X86-64 flags handling broken List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: Bug 1156313 <1156313@bugs.launchpad.net>, qemu-devel@nongnu.org --=-=-= Richard Henderson writes: Patch at http://patchwork.ozlabs.org/patch/229139/ Thanks. I can confirm that this fixes the bug triggered by my test case (and yours). However, the instability of Debian GNU/Linux x86_64 has not improved. The exact same Debian version (debian "testing") updated at the same time runs well on hardware. My qemu Debian system now got messed up, since I attempted an upgrade in the buggy qemu, which segfaulted several times during the upgrade. I need to reinstall, and then rely on -snapshot. There is a problem with denorms which is reproducible, but whether that is a qemu bug, and whether it can actually cause the observed instability, is questionable. Here is a testcase for that problem: --=-=-= Content-Type: application/octet-stream Content-Disposition: attachment; filename=qemu-denorm-problem.s .text .globl main .type main, @function main: mov $0x10000000000000, %rax # DBL_MIN movq %rax, %xmm0 movabsq $0x4000000000000000, %rax # 2.0 movq %rax, %xmm1 divsd %xmm1, %xmm0 xorpd %xmm1, %xmm1 1: ucomisd %xmm0, %xmm1 je 1b mov $0, %eax ret .size main, .-main --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable It should terminate. The observed buggy behaviour is that it hangs. The instability problem can be observed at gmplib.org/devel/tm-date.html. hwl-deb.gmplib.org is Debian under qemu with -cpu Haswell,+adx. Not that the exact same qemu runs FreeBSD flawlessly (hwl.gmplib.org). It is neither instable nor does it run the denorms testcase poorly. I fully realise this is a hopeless bug report, but I am sure you can reproduce it, since it is far from GMP specific. After all apt-get update; apt-get upgrade triggered it. Debugging it will be a nightmare. Qemu version: main git repo from less than a week ago + Richard ADX patch. --=20 Torbj=C3=B6rn --=-=-=--