Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754177AbYGYPN1 (ORCPT ); Fri, 25 Jul 2008 11:13:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751198AbYGYPNS (ORCPT ); Fri, 25 Jul 2008 11:13:18 -0400 Received: from dgate20.fujitsu-siemens.com ([80.70.172.51]:40893 "EHLO dgate20.fujitsu-siemens.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751349AbYGYPNR (ORCPT ); Fri, 25 Jul 2008 11:13:17 -0400 DomainKey-Signature: s=s768; d=fujitsu-siemens.com; c=nofws; q=dns; h=X-SBRSScore:X-IronPort-AV:Received:X-IronPort-AV: Received:Received:Message-ID:Date:From:Organization: User-Agent:MIME-Version:To:CC:Subject:References: In-Reply-To:Content-Type; b=CK5Lw+u2ADM47cVnXo/IPai447bv3xUN9pZrmCwMv3zsX3ISDSCe65RT PNidkvOSJrZcWRc81QcjHJfwmzSyC3WL8FRgqozARAgXvBRt6m5847T8W GE+v4EnuCwnV5pF; X-SBRSScore: None X-IronPort-AV: E=Sophos;i="4.31,252,1215381600"; d="diff'?scan'208";a="21235800" X-IronPort-AV: E=Sophos;i="4.31,252,1215381600"; d="diff'?scan'208";a="32955967" Message-ID: <4889ED91.7050800@fujitsu-siemens.com> Date: Fri, 25 Jul 2008 17:13:21 +0200 From: Martin Wilck Organization: Fujitsu Siemens Computers User-Agent: Thunderbird 2.0.0.15pre (X11/20080508) MIME-Version: 1.0 To: Cyrill Gorcunov CC: Thomas Gleixner , "linux-kernel@vger.kernel.org" , "H. Peter Anvin" , "Wichert, Gerhard" , "Maciej W. Rozycki" Subject: Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe (take 3) References: <20080724143151.GA32422@lenovo> <20080724150116.GC32422@lenovo> <48889C14.4070408@fujitsu-siemens.com> <4889968E.6020000@fujitsu-siemens.com> <20080725100844.GA16698@lenovo> <4889C723.7050402@fujitsu-siemens.com> <20080725125950.GA28466@lenovo> <4889D767.5050709@fujitsu-siemens.com> <20080725134831.GB28466@lenovo> <4889DCA4.4010800@fujitsu-siemens.com> <20080725150104.GD28466@lenovo> In-Reply-To: <20080725150104.GD28466@lenovo> Content-Type: multipart/mixed; boundary="------------060209070302030003050102" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4176 Lines: 134 This is a multi-part message in MIME format. --------------060209070302030003050102 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cyrill Gorcunov wrote: > Martin, it seems you forgot to attach the patch :) I am sorry, here it is. Thanks :) Martin -- Martin Wilck PRIMERGY System Software Engineer FSC IP ESP DEV 6 Fujitsu Siemens Computers GmbH Heinz-Nixdorf-Ring 1 33106 Paderborn Germany Tel: ++49 5251 8 15113 Fax: ++49 5251 8 20209 Email: mailto:martin.wilck@fujitsu-siemens.com Internet: http://www.fujitsu-siemens.com Company Details: http://www.fujitsu-siemens.com/imprint.html --------------060209070302030003050102 Content-Type: text/x-patch; name="calibrate_APIC_clock-4a.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="calibrate_APIC_clock-4a.diff" [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe (take 3) Non-maskable asynchronous events (e.g. SMIs) which occur during the APIC timer calibration can cause timer miscalibrations, sometimes by large amounts. This patch fixes this by making sure that no significant interruption occurs between APIC and TSC reads. SMIs may still occur at some stage in the calibration loop, causing the loop to last longer than intended. This doesn't matter though, as long as the start and end values are both taken simultaneously. Changed wrt take 2: Use max. possible start value for the APIC timer to avoid underflow. Signed-off-by: Martin Wilck Signed-off-by: Gerhard Wichert --- arch/x86/kernel/apic_64.c 2008-07-25 15:39:51.000000000 +0200 +++ arch/x86/kernel/apic_64.c.new 2008-07-25 15:55:08.000000000 +0200 @@ -300,6 +300,31 @@ static void setup_APIC_timer(void) } /* + * Helper function for calibrate_APIC_clock(): Make sure that + * APIC TMCTT and TSC are read at the same time, to reasonable + * accuracy. On any sane system, the retry loop won't need more + * than a single retry, given that the rdtsc/apic_read/rdtsc + * sequence won't take more than a few cycles. + */ + +#define MAX_DIFFERENCE 1000UL +#define MAX_ITER 10 +static inline int +__read_tsc_and_apic(unsigned long *tsc, unsigned *apic) +{ + unsigned long tsc0, tsc1, diff; + int i = 0; + do { + rdtscll(tsc0); + *apic = apic_read(APIC_TMCCT); + rdtscll(tsc1); + diff = tsc1 - tsc0; + } while (diff > MAX_DIFFERENCE && ++i < MAX_ITER); + *tsc = tsc0 + (diff >> 1); + return diff > MAX_DIFFERENCE ? -EIO : 0; +} + +/* * In this function we calibrate APIC bus clocks to the external * timer. Unfortunately we cannot use jiffies and the timer irq * to calibrate, since some later bootup code depends on getting @@ -318,7 +343,7 @@ static void __init calibrate_APIC_clock( { unsigned apic, apic_start; unsigned long tsc, tsc_start; - int result; + int result, err_start, err; local_irq_disable(); @@ -329,25 +354,27 @@ static void __init calibrate_APIC_clock( * * No interrupt enable ! */ - __setup_APIC_LVTT(250000000, 0, 0); + __setup_APIC_LVTT(0xffffffff, 0, 0); - apic_start = apic_read(APIC_TMCCT); #ifdef CONFIG_X86_PM_TIMER if (apic_calibrate_pmtmr && pmtmr_ioport) { + apic_start = apic_read(APIC_TMCCT); pmtimer_wait(5000); /* 5ms wait */ apic = apic_read(APIC_TMCCT); result = (apic_start - apic) * 1000L / 5; } else #endif { - rdtscll(tsc_start); + err_start = __read_tsc_and_apic(&tsc_start, &apic_start); do { - apic = apic_read(APIC_TMCCT); - rdtscll(tsc); + err = __read_tsc_and_apic(&tsc, &apic); } while ((tsc - tsc_start) < TICK_COUNT && (apic_start - apic) < TICK_COUNT); + if (err_start || err) + printk(KERN_CRIT "calibrate_APIC_clock: SMI flood - " + "the APIC timer calibration may be wrong!\n"); result = (apic_start - apic) * 1000L * tsc_khz / (tsc - tsc_start); } --------------060209070302030003050102-- -- 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/