From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: Debugging an inconsistent shadow page table Date: Sun, 26 Apr 2009 13:41:27 +0200 Message-ID: <49F44867.3010008@web.de> References: <49F2E79A.6070602@web.de> <49F43846.40807@redhat.com> <49F4416C.4090204@web.de> <20090426112749.GT24095@redhat.com> <49F44736.6000001@web.de> <20090426113952.GU24095@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig7D6FF2345EAF4818EFB23C32" Cc: Avi Kivity , kvm-devel To: Gleb Natapov Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:51551 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbZDZLmP (ORCPT ); Sun, 26 Apr 2009 07:42:15 -0400 In-Reply-To: <20090426113952.GU24095@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig7D6FF2345EAF4818EFB23C32 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Sun, Apr 26, 2009 at 01:36:22PM +0200, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Sun, Apr 26, 2009 at 01:11:40PM +0200, Jan Kiszka wrote: >>>> That raise a question for a kvm-mmu newbie like me: >>>> >>>> If a page of the qemu process gets pushed around (here likely due to= >>>> fork()->exec(smbd)->COW), how will kvm's shadow table catch up? Via >>>> MMU_NOTIFIER? >>>> >>>> I'm on a 2.6.25 kernel, and that means without CONFIG_MMU_NOTIFIER. = So >>>> far I assumed that kernels without this feature do not work optimall= y, >>>> but they won't break my guests... >>>> >>> Guest memory is not COWed on fork (madvise(MADV_DONTFORK)) >> Yeah... but that's missing upstream! Will cross-check and then post a >> fix for qemu. >> >> Out of curiosity: What's the mechanism to update the shadow table afte= r >> swap-out/swap-in? >> > I don't think guest memory is swappable without mmu notifiers.=20 Given the experience with COW: How is this ensured, or where is this done upstream? Jan --------------enig7D6FF2345EAF4818EFB23C32 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 iEYEARECAAYFAkn0SGcACgkQniDOoMHTA+mcZwCfYJY8+W8mZN5tkvJzJ4cm0yWa YsEAn16RnWoAJ51BQ8l2d9OkIrQtreQd =C4St -----END PGP SIGNATURE----- --------------enig7D6FF2345EAF4818EFB23C32--