From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753347AbZBTFDM (ORCPT ); Fri, 20 Feb 2009 00:03:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750715AbZBTFC4 (ORCPT ); Fri, 20 Feb 2009 00:02:56 -0500 Received: from mga11.intel.com ([192.55.52.93]:44138 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750698AbZBTFC4 (ORCPT ); Fri, 20 Feb 2009 00:02:56 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.38,238,1233561600"; d="asc'?scan'208";a="667080629" Subject: Re: [git pull] changes for tip, and a nasty x86 page table bug From: Huang Ying To: Linus Torvalds Cc: Steven Rostedt , Thomas Gleixner , Ingo Molnar , Linux Kernel Mailing List , Andrew Morton , Peter Zijlstra , Frederic Weisbecker , Arjan van de Ven , Rusty Russell , Mathieu Desnoyers , "H. Peter Anvin" In-Reply-To: References: <20090220011316.379904625@goodmis.org> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-O1DiMTcFbuaPg/VDMg4Z" Date: Fri, 20 Feb 2009 13:02:52 +0800 Message-Id: <1235106172.6171.63.camel@yhuang-dev.sh.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-O1DiMTcFbuaPg/VDMg4Z Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Hi, Linus, On Fri, 2009-02-20 at 12:17 +0800, Linus Torvalds wrote: >=20 > On Thu, 19 Feb 2009, Steven Rostedt wrote: > >=20 > > Is this something worthy of 29? I could whip up a patch against your=20 > > latest tree. >=20 > I think it's a real issue, but I do have to admit that I don't see why it= =20 > would only trigegr for you. Is it just because the trace stuff ends up=20 > setting pages to RW, and you have to have had a lot of read-only stuff to= =20 > get a whole read-only PMD to begin with? >=20 > So there's two things that make me nervous: >=20 > - I do think the KERNPG_TABLE thing is the right thing, and I _think_=20 > that code is just confused, and we should just do KERNPG_TABLE rather=20 > than play with confused bits one by one (PRESENT, RW, NX) to the point= =20 > of just making for more confusion. >=20 > But I'd like some of the people involved with that code confirm that.=20 > Either a "Yeah, we were just confused" or "No, there's this really=20 > subtle thing going on, liek this: ..." >=20 > - The fact that apparently you're the first one to hit this. I realize=20 > that you do odd things with ftrace. Was it the fact that you made the=20 > "set_memory_ro()" area larger, and then more dynamically mark it back=20 > to read-write that you hit it? Haven't we done things like that before= ? In fact, I am the first one to hit a similar bug. I do some odd thing with EFI to change the page tables to be executable. Unfortunately I fixed that bug in a confused way. Yes. I think KERNPG_TABLE fixes all these types of bugs in a more clear way. Best Regards, Huang Ying --=-O1DiMTcFbuaPg/VDMg4Z Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAkmeOXcACgkQKhFGF+eHlpj41ACeIUug86xiKghBTBAtVhbX3vtt F/UAnAtc3eRqROL2PNa5Re8wEWVGerJZ =F5sJ -----END PGP SIGNATURE----- --=-O1DiMTcFbuaPg/VDMg4Z--