Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755417AbcKOFbS (ORCPT ); Tue, 15 Nov 2016 00:31:18 -0500 Received: from mail-qt0-f181.google.com ([209.85.216.181]:34251 "EHLO mail-qt0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755263AbcKOFbQ (ORCPT ); Tue, 15 Nov 2016 00:31:16 -0500 MIME-Version: 1.0 In-Reply-To: <45DE3A97-304D-4D1A-AADE-1B9D154BB7DF@gmail.com> References: <45DE3A97-304D-4D1A-AADE-1B9D154BB7DF@gmail.com> From: Dmitry Vyukov Date: Tue, 15 Nov 2016 06:30:53 +0100 Message-ID: Subject: Re: kvm: WARNING in em_jmp_far To: syzkaller Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "x86@kernel.org" , KVM list , LKML , Steve Rutherford , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uAF5VOnq025274 Content-Length: 974 Lines: 26 On Tue, Nov 15, 2016 at 6:24 AM, Nadav Amit wrote: > >> On Nov 14, 2016, at 9:06 PM, Dmitry Vyukov wrote: >> >> Hello, >> >> The following program triggers WARNING in em_jmp_far: >> https://gist.githubusercontent.com/dvyukov/16bfd3d68fa7d5461101ef74e07796e4/raw/e6d663980681f2c5838ff6cd361cede7d3204838/gistfile1.txt >> >> >> WARNING: CPU: 1 PID: 15748 at arch/x86/kvm/emulate.c:2128 em_jmp_far+0x4a7/0x530 > > I don’t know how to “read” the test, but it seems that this warning > can be triggered if CS base/limit cause a #GP exception when EIP > is loaded. > > I think it safe to remove this warning (which I introduced) as well as > the redundant “return rc” that follows it. The code should handle the > emulation correctly regardless of the warning. There was also a similar WARNING in em_ret_far: https://groups.google.com/forum/#!msg/syzkaller/o5ZftARBhrs/r1ivQ-HtBgAJ Please mail a fix and add a test. Thanks