From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753015AbaF2LAK (ORCPT ); Sun, 29 Jun 2014 07:00:10 -0400 Received: from mout.web.de ([212.227.17.12]:52678 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752877AbaF2LAI (ORCPT ); Sun, 29 Jun 2014 07:00:08 -0400 Message-ID: <53AFF192.7020801@web.de> Date: Sun, 29 Jun 2014 12:59:30 +0200 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Gleb Natapov CC: Borislav Petkov , Paolo Bonzini , lkml , Peter Zijlstra , Steven Rostedt , x86-ml , kvm@vger.kernel.org, =?ISO-8859-1?Q?J=F6rg_R=F6?= =?ISO-8859-1?Q?del?= Subject: Re: __schedule #DF splat References: <20140627101831.GB23153@pd.tnic> <53AD586A.40900@redhat.com> <20140627115545.GC23153@pd.tnic> <53AD5D27.2090505@redhat.com> <20140627121053.GD23153@pd.tnic> <20140628114431.GB4373@pd.tnic> <20140629064626.GD18167@minantech.com> <53AFE2B3.5080300@web.de> <20140629102403.GE18167@minantech.com> <53AFEB16.5040608@web.de> <20140629105339.GF18167@minantech.com> In-Reply-To: <20140629105339.GF18167@minantech.com> X-Enigmail-Version: 1.6 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="1bltKXRgKGRo6fbMlScKxr3tmt2AL7WqI" X-Provags-ID: V03:K0:PYj41/hn9Qyw6VLLleVIvgTz+OFlyJsqwOY80ExMvSvcC17Jojk +iBpMTox7Qc5gQbhwK3IfNC4dF6VGfPXzYc5v2Sbrgtl2kVyCApaS8VPEuxNYNuh9GgHJHK hR/QxnQLCaUAUVKUMDfPESvgxFCLn+jCiCnoFo5iIwI9VxE96XgInPoNJe1kudrUZAT6M+r cobK68EiNIV05MT218nDQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --1bltKXRgKGRo6fbMlScKxr3tmt2AL7WqI Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2014-06-29 12:53, Gleb Natapov wrote: > On Sun, Jun 29, 2014 at 12:31:50PM +0200, Jan Kiszka wrote: >> On 2014-06-29 12:24, Gleb Natapov wrote: >>> On Sun, Jun 29, 2014 at 11:56:03AM +0200, Jan Kiszka wrote: >>>> On 2014-06-29 08:46, Gleb Natapov wrote: >>>>> On Sat, Jun 28, 2014 at 01:44:31PM +0200, Borislav Petkov wrote: >>>>>> qemu-system-x86-20240 [006] ...1 9406.484134: kvm_page_fault: ad= dress 7fffb62ba318 error_code 2 >>>>>> qemu-system-x86-20240 [006] ...1 9406.484136: kvm_inj_exception:= #PF (0x2)a >>>>>> >>>>>> kvm injects the #PF into the guest. >>>>>> >>>>>> qemu-system-x86-20240 [006] d..2 9406.484136: kvm_entry: vcpu 1 >>>>>> qemu-system-x86-20240 [006] d..2 9406.484137: kvm_exit: reason P= F excp rip 0xffffffff8161130f info 2 7fffb62ba318 >>>>>> qemu-system-x86-20240 [006] ...1 9406.484138: kvm_page_fault: ad= dress 7fffb62ba318 error_code 2 >>>>>> qemu-system-x86-20240 [006] ...1 9406.484141: kvm_inj_exception:= #DF (0x0) >>>>>> >>>>>> Second #PF at the same address and kvm injects the #DF. >>>>>> >>>>>> BUT(!), why? >>>>>> >>>>>> I probably am missing something but WTH are we pagefaulting at a >>>>>> user address in context_switch() while doing a lockdep call, i.e. >>>>>> spin_release? We're not touching any userspace gunk there AFAICT. >>>>>> >>>>>> Is this an async pagefault or so which kvm is doing so that the gu= est >>>>>> rip is actually pointing at the wrong place? >>>>>> >>>>> There is nothing in the trace that point to async pagefault as far = as I see. >>>>> >>>>>> Or something else I'm missing, most probably... >>>>>> >>>>> Strange indeed. Can you also enable kvmmmu tracing? You can also in= strument >>>>> kvm_multiple_exception() to see which two exception are combined in= to #DF. >>>>> >>>> >>>> FWIW, I'm seeing the same issue here (likely) on an E-450 APU. It >>>> disappears with older KVM (didn't bisect yet, some 3.11 is fine) and= >>>> when patch-disabling the vmport in QEMU. >>>> >>>> Let me know if I can help with the analysis. >>>> >>> Bisection would be great of course. Once thing that is special about >>> vmport that comes to mind is that it reads vcpu registers to userspac= e and >>> write them back. IIRC "info registers" does the same. Can you see if = the >>> problem is reproducible with disabled vmport, but doing "info registe= rs" >>> in qemu console? Although trace does not should any exists to userspa= ce >>> near the failure... >> >> Yes, info registers crashes the guest after a while as well (with >> different backtrace due to different context). >> > Oh crap. Bisection would be most helpful. Just to be absolutely sure > that this is not QEMU problem: does exactly same QEMU version work with= > older kernels? Yes, that was the case last time I tried (I'm on today's git head with QEMU right now). Will see what I can do regarding bisecting. That host is a bit slow (netbook), so it may take a while. Boris will probably beat me in this. Jan --1bltKXRgKGRo6fbMlScKxr3tmt2AL7WqI Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlOv8ZIACgkQitSsb3rl5xT5PQCgzX/SdxjKFM14322WGkSmaBER rJ0AoKMgSEv6h5aClYGz4yX4vo9fJad3 =WrTX -----END PGP SIGNATURE----- --1bltKXRgKGRo6fbMlScKxr3tmt2AL7WqI--