Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752605AbbEFI2J (ORCPT ); Wed, 6 May 2015 04:28:09 -0400 Received: from mail-wg0-f66.google.com ([74.125.82.66]:34277 "EHLO mail-wg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbbEFI2D (ORCPT ); Wed, 6 May 2015 04:28:03 -0400 From: Ingo Molnar X-Google-Original-From: Ingo Molnar Date: Wed, 6 May 2015 10:27:59 +0200 To: Jan =?iso-8859-1?Q?H=2E_Sch=F6nherr?= Cc: Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org, Anthony Liguori , Ingo Molnar , "H. Peter Anvin" , Tim Deegan , Gang Wei , Linus Torvalds , Len Brown Subject: Re: [PATCH] x86: skip delays during SMP initialization similar to Xen Message-ID: <20150506082759.GA30019@gmail.com> References: <1430732554-7294-1-git-send-email-jschoenh@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1430732554-7294-1-git-send-email-jschoenh@amazon.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2440 Lines: 64 * Jan H. Sch?nherr wrote: > Remove the per-CPU delays during SMP initialization, which seems to be > possible on newer architectures with an x2APIC. > > Xen does this since 2011. In fact, this commit is basically a > combination of the following Xen commits. The first removes the delays, > the second fixes an issue with the removal: > > commit 68fce206f6dba9981e8322269db49692c95ce250 > Author: Tim Deegan > Date: Tue Jul 19 14:13:01 2011 +0100 > > x86: Remove timeouts from INIT-SIPI-SIPI sequence when using x2apic. > > Some of the timeouts are pointless since they're waiting for the ICR > to ack the IPI delivery and that doesn't happen on x2apic. > The others should be benign (and are suggested in the SDM) but > removing them makes AP bringup much more reliable on some test boxes. > > Signed-off-by: Tim Deegan > > commit f12ee533150761df5a7099c83f2a5fa6c07d1187 > Author: Gang Wei > Date: Thu Dec 29 10:07:54 2011 +0000 > > X86: Add a delay between INIT & SIPIs for tboot AP bring-up in X2APIC case > > Without this delay, Xen could not bring APs up while working with > TXT/tboot, because tboot needs some time in APs to handle INIT before > becoming ready for receiving SIPIs (this delay was removed as part of > c/s 23724 by Tim Deegan). > > Signed-off-by: Gang Wei > Acked-by: Keir Fraser > Acked-by: Tim Deegan > Committed-by: Tim Deegan > > Signed-off-by: Jan H. Sch?nherr > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: H. Peter Anvin > Cc: Tim Deegan > Cc: Gang Wei > --- > arch/x86/kernel/smpboot.c | 61 +++++++++++++++++++++++++++++------------------ > 1 file changed, 38 insertions(+), 23 deletions(-) > > This patch is against Linux 4.1-rc1. So I really like this, as it nicely side-steps the 'when should we do the legacy delays' issue by flagging on x2apic support. If anyone has objections, please holler. Thanks, Ingo -- 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/