From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp Date: Sun, 07 Mar 2010 11:48:33 +0100 Message-ID: <4B938481.70307@web.de> References: <20100303160022.GG16909@redhat.com> <4B8EF1FE.7020000@web.de> <20100304064723.GH16909@redhat.com> <4B8F6E12.8040707@web.de> <20100304083549.GI16909@redhat.com> <4B8F9B11.60804@siemens.com> <20100304120354.GK16909@redhat.com> <20100307063643.GN16909@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig9DA2F7C0BA676188B07ACDB2" Cc: Avi Kivity , Marcelo Tosatti , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" To: Gleb Natapov Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:40217 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750821Ab0CGKt5 (ORCPT ); Sun, 7 Mar 2010 05:49:57 -0500 In-Reply-To: <20100307063643.GN16909@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig9DA2F7C0BA676188B07ACDB2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Thu, Mar 04, 2010 at 02:03:54PM +0200, Gleb Natapov wrote: >>> BTW, do real systems allow to hot plug BSP as well? Or how is the cas= e >>> handled when you unplug the BSP and then reboot the box? >>> >> Did you mean hot unplug BSP? OS determines what CPU is BSP by checking= >> BSP bit in APIC base register. My guess is that there is some pin on C= PU >> which value is mirrored as BSP bit in APIC base register. Board may ha= ve >> some logic to check what sockets are populated and chose one of them a= s >> BSP by pulling its pin up. But this is only guess. >> > Actually this is much more simple: > SDM 8.4.1: > The MP initialization protocol defines two classes of processors: the > bootstrap processor (BSP) and the application processors (APs). Follow= ing > a power-up or RESET of an MP system, system hardware dynamically selec= ts > one of the processors on the system bus as the BSP. The remaining > processors are designated as APs. > And by "hardware" they mean CPUs themselves over apic BUS. That should be straightforward, will have a look. I just want to ensure that cpu_is_bsp delivers a valid result all the time. Otherwise we will run into ordering issues again once some new user of this services shows = up. Jan --------------enig9DA2F7C0BA676188B07ACDB2 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 iEYEARECAAYFAkuThIUACgkQitSsb3rl5xR3oQCdHFiTGsr5F1hB/B2kbKMRf1Qp FLUAoN3gKSyIEHbWcR1avQe+3Rz0LKYm =JQc6 -----END PGP SIGNATURE----- --------------enig9DA2F7C0BA676188B07ACDB2--