Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752672AbaBNSXg (ORCPT ); Fri, 14 Feb 2014 13:23:36 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:32812 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951AbaBNSXf (ORCPT ); Fri, 14 Feb 2014 13:23:35 -0500 Message-ID: <52FE5F0C.5000901@canonical.com> Date: Fri, 14 Feb 2014 19:23:08 +0100 From: Stefan Bader User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Borislav Petkov CC: Peter Zijlstra , Paolo Bonzini , Linux Kernel Mailing List , kvm@vger.kernel.org, Marcelo Tosatti , MASAO TAKAHASHI , Joerg Roedel Subject: Re: Another preempt folding issue? References: <52FB5669.7090506@canonical.com> <20140212115412.GW27965@twins.programming.kicks-ass.net> <52FCFA23.4060701@canonical.com> <20140213173852.GH6835@laptop.programming.kicks-ass.net> <52FD090C.7010408@canonical.com> <20140213182605.GC14089@laptop.programming.kicks-ass.net> <20140214133428.GB26356@pd.tnic> <52FE2709.3050505@canonical.com> <20140214144700.GC26356@pd.tnic> <52FE4C28.1080500@canonical.com> <20140214173333.GA6953@pd.tnic> In-Reply-To: <20140214173333.GA6953@pd.tnic> X-Enigmail-Version: 1.5.2 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="9LEPuv2Fs5bodd6i64UP2OR0ljvu9gIUo" 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) --9LEPuv2Fs5bodd6i64UP2OR0ljvu9gIUo Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 14.02.2014 18:33, Borislav Petkov wrote: > On Fri, Feb 14, 2014 at 06:02:32PM +0100, Stefan Bader wrote: >> Okaaay, I think I did what you asked. So yes, there is sse2 in the cpu= info. And >> there is a mfence in the disassembly: >=20 > Btw, I just realized booting the kernel in the guest was a dumb idea, > because, doh, the guest is not baremetal. The only reliable thing we > can say is that sse2 is present and that MFENCE alternative replacement= > works :) >=20 > But for simplicity's sake let's just assume the machine can do MFENCE > just fine and it gets replaced by the alternatives code. >=20 > Besides, if that weren't true, we'd have a whole lot of other problems > on those boxes. >=20 >> Thinking about it, I guess Peter is quite right saying that I likely >> will end on the patch that converted preempt_count to percpu. >=20 > Yeah, c2daa3bed53a81171cf8c1a36db798e82b91afe8 et al. >=20 >> One thing I likely should do is to reinstall the exact same laptop >> with 64bit kernel and userspace... maybe only 64bit kernel first... >> and make sure on my side that this does not show up on 64bit, too. I >> took the word of reporters for that (and the impression that otherwise= >> many more people would have complained). >=20 > Yeah, that should be a prudent thing to do. >=20 > Also, Paolo and I were wondering whether you can trigger this thing > without kvm, i.e. virtualization involved... do you have any data on > that? Unfortunately no hard evidence. Kvm just happens to be such a good way to= notice this as it is using the reschedule interrupt itself and has this exit bef= ore running the guest vcpu to hadnle it in the outer loop by calling cond_res= ched() and repeat. I find running kvm seems to make that laptop quite sluggish in responding= to other tasks (in that install) and I got some oddness going on when lightd= m quite often refuses to take keyboard input without opening some menu with the m= ouse first... But I could not be sure whether that is the kernel or some new user-space ... errr "feature". At least Marcello (iirc that other report came from him directly or indir= ectly) has seen it, too. And he likely has complete different user-space. So I will go and do that different (64bit) kernel and kernel + user-space= test. But like fo Peter, it likely is a Monday thing... --9LEPuv2Fs5bodd6i64UP2OR0ljvu9gIUo Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBCgAGBQJS/l8MAAoJEOhnXe7L7s6jt94QANuG1p6VLcwoCG1+sH6EJyvd 2Y3O4PY4DSFcX6yOgR8rI21flKeLKf7KsK9J7Y+GyGH3QedowJXxjQ3DcqudBJGe 4f4fxOIrShlwNptpByd/QFp2Mo29eUL7C7+WLUw0z3z7UyDRiuCmlW+jwaRh4+uF IyoS7vQCBzCVxU27kBpUvEEA1aAbTsjRN3JEMrfWe0aVYKk/RSh3RpmrRJSN9y6q 1KQ+mGnbyisXgnYfiDvRoFX3hiQud2PWkWgTFQkSB5QyeVoUrZHKZYsJuz8pIKGe p5T260ABDbktn9gN1z/dWiFt3Ss6Any6d8sqXO2yc2pv1IZcjC5l08M4s0RdM+PX eGGEOdhNL+VJRaeR9+j43vGk3i4M7CWQM4nhH22qYOnVN+m4zn1YZlH/0Sp5XFD1 X+peKzO7ePrZv5BhdG53leEFiPlAAarIXYtC7Gd8zX3NUCbOHjkY8f70XTaNTHep 7ej/MOguPRvUAsHkptz5LNkXjaQHeGGHeLTGYT0bpgJ+ju9SEXY5DCh7xxO3DfOA TQxIUGVwnDab8XKtFHODBtMoLyaFf7gRVGSdWaRagjm0KRNIPdr6y+2ZjCTHe2TG wossOsOM/CXLBNyK4NgWjVZIvLaL0dfoKffAui8b5UK35seLDQO55rVKZm6Hphte qcos/47OyJ0xsOARKrIK =DClF -----END PGP SIGNATURE----- --9LEPuv2Fs5bodd6i64UP2OR0ljvu9gIUo-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/