From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: __schedule #DF splat Date: Sun, 29 Jun 2014 11:56:03 +0200 Message-ID: <53AFE2B3.5080300@web.de> References: <20140625153227.GA13845@pd.tnic> <20140625202650.GC13845@pd.tnic> <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> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="QAlNSXRhDWBOxdsN6aCdxLJ5exSqeNqcc" Cc: 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?= To: Gleb Natapov , Borislav Petkov Return-path: Received: from mout.web.de ([212.227.15.4]:54286 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752485AbaF2J5q (ORCPT ); Sun, 29 Jun 2014 05:57:46 -0400 In-Reply-To: <20140629064626.GD18167@minantech.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --QAlNSXRhDWBOxdsN6aCdxLJ5exSqeNqcc Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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: addres= s 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 PF ex= cp rip 0xffffffff8161130f info 2 7fffb62ba318 >> qemu-system-x86-20240 [006] ...1 9406.484138: kvm_page_fault: addres= s 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 guest >> rip is actually pointing at the wrong place? >> > There is nothing in the trace that point to async pagefault as far as I= see. >=20 >> Or something else I'm missing, most probably... >> > Strange indeed. Can you also enable kvmmmu tracing? You can also instru= ment > kvm_multiple_exception() to see which two exception are combined into #= DF. >=20 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. Jan --QAlNSXRhDWBOxdsN6aCdxLJ5exSqeNqcc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlOv4rsACgkQitSsb3rl5xTV9QCfU62QxfAbivpi6MpMrwsvdoyX BYoAoIjqwFqgdjT0GRpjsAJMP7gSRrGk =2iA4 -----END PGP SIGNATURE----- --QAlNSXRhDWBOxdsN6aCdxLJ5exSqeNqcc--