From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Debugging an inconsistent shadow page table Date: Sat, 25 Apr 2009 12:36:10 +0200 Message-ID: <49F2E79A.6070602@web.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigA7A9D0E0A5A2B5BE6156ECDD" To: kvm-devel Return-path: Received: from fmmailgate01.web.de ([217.72.192.221]:50953 "EHLO fmmailgate01.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751562AbZDYKgR (ORCPT ); Sat, 25 Apr 2009 06:36:17 -0400 Received: from smtp06.web.de (fmsmtp06.dlan.cinetic.de [172.20.5.172]) by fmmailgate01.web.de (Postfix) with ESMTP id 16B48100A50BA for ; Sat, 25 Apr 2009 12:36:16 +0200 (CEST) Received: from [88.65.38.201] (helo=[192.168.1.123]) by smtp06.web.de with asmtp (TLSv1:AES256-SHA:256) (WEB.DE 4.110 #277) id 1LxfF1-0008T0-00 for kvm@vger.kernel.org; Sat, 25 Apr 2009 12:36:16 +0200 Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigA7A9D0E0A5A2B5BE6156ECDD Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Hi, turning on MMU_DEBUG and AUDIT in arch/x86/kvm/mmu.c (and fixing a build error, patch will follow) I got this (and then a #GP :( - patch will follow): =2E.. kvm_mmu_get_page: looking gfn 0 role f0120 kvm_mmu_get_page: found kvm_mmu_get_page: looking gfn 0 role f0220 kvm_mmu_get_page: found kvm_mmu_get_page: looking gfn 0 role f0320 kvm_mmu_get_page: found kvm_mmu_get_page: looking gfn e1f role e0044 kvm_mmu_get_page: adding gfn e1f role e0044 rmap_write_protect: spte ffff8100660a60f8 7ca98067 paging64_page_fault: addr 100105 err 19 audit_write_protection: (pre page fault) shadow page has writable mapping= s: gfn e1f role e0044 audit: (pre page fault) nontrapping pte in nonleaf level: levels 4 gva 80= 00000000 level 4 pte 0 Is the last message indicating a problem? I get it very early during guest boot. oos_shadow is disabled. I'm currently trying to understand an obvious inconsistency in the pte describing a page of the virtio-net rx ring. On some guests with some qemu (upstream) command lines I can trigger this with '-smb /some/path' and then doing smbclient -L in the guest. Once the inconsistency slipped in, host and guest see different page contents and virtio-net stops to work. Very strange, but fortunately easily reproducible here. Any hints or debugging suggestions welcome! Jan --------------enigA7A9D0E0A5A2B5BE6156ECDD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkny554ACgkQniDOoMHTA+mlhACfaRICYlbJnvoTAl0HZRDQ23Zp RmEAnih30u8jCLgB3bvv6UE3iNESdZIy =3xYG -----END PGP SIGNATURE----- --------------enigA7A9D0E0A5A2B5BE6156ECDD--