Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755492AbWKPWx4 (ORCPT ); Thu, 16 Nov 2006 17:53:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755493AbWKPWx4 (ORCPT ); Thu, 16 Nov 2006 17:53:56 -0500 Received: from smtp.osdl.org ([65.172.181.4]:12773 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1755492AbWKPWxy (ORCPT ); Thu, 16 Nov 2006 17:53:54 -0500 Date: Thu, 16 Nov 2006 14:53:13 -0800 From: Andrew Morton To: Zachary Amsden Cc: Rusty Russell , Andi Kleen , Jeremy Fitzhardinge , Chris Wright , Virtualization Mailing List , Linux Kernel Mailing List Subject: Re: [PATCH 1/5] Skip timer works.patch Message-Id: <20061116145313.d7b2240b.akpm@osdl.org> In-Reply-To: <200610200009.k9K09MrS027558@zach-dev.vmware.com> References: <200610200009.k9K09MrS027558@zach-dev.vmware.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5389 Lines: 145 On Thu, 19 Oct 2006 17:09:22 -0700 Zachary Amsden wrote: > Add a way to disable the timer IRQ routing check via a boot option. The > VMI timer code uses this to avoid triggering the pester Mingo code, which > probes for some very unusual and broken motherboard routings. It fires > 100% of the time when using a paravirtual delay mechanism instead of > using a realtime delay, since there is no elapsed real time, and the 4 timer > IRQs have not yet been delivered. > > In addition, it is entirely possible, though improbable, that this bug > could surface on real hardware which picks a particularly bad time to enter > SMM mode, causing a long latency during one of the timer IRQs. > > While here, make check_timer be __init. > Andi seems to have merged this patch but from somewhere I picked up a different version, below. I think the version I have is better. Because the patch Andi has merged is cast in terms of "irq testing", which is broad. But that's not what the patch does - the patch handles only timers. IOW, this: > + > + noirqtest [IA-32,APIC] Disables the code which tests for broken > + timer IRQ sources. is misleadingly named. This: + no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for + broken timer IRQ sources. + is better, no? But right now, I'll settle for anything which usually compiles. From: Zachary Amsden Add a way to disable the timer IRQ routing check via a boot option. The VMI timer code uses this to avoid triggering the pester Mingo code, which probes for some very unusual and broken motherboard routings. It fires 100% of the time when using a paravirtual delay mechanism instead of using a realtime delay, since there is no elapsed real time, and the 4 timer IRQs have not yet been delivered. In addition, it is entirely possible, though improbable, that this bug could surface on real hardware which picks a particularly bad time to enter SMM mode, causing a long latency during one of the timer IRQs. While here, make check_timer be __init. Signed-off-by: Zachary Amsden [chrisw: use no_timer_check to bring inline with x86_64 as per Andi's request] Signed-off-by: Chris Wright Cc: Andi Kleen Signed-off-by: Andrew Morton --- Documentation/kernel-parameters.txt | 7 +++++-- arch/i386/kernel/io_apic.c | 16 ++++++++++++++-- 2 files changed, 19 insertions(+), 4 deletions(-) diff -puN arch/i386/kernel/io_apic.c~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option arch/i386/kernel/io_apic.c --- a/arch/i386/kernel/io_apic.c~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option +++ a/arch/i386/kernel/io_apic.c @@ -1930,6 +1930,15 @@ static void __init setup_ioapic_ids_from static void __init setup_ioapic_ids_from_mpc(void) { } #endif +static int no_timer_check __initdata; + +static int __init notimercheck(char *s) +{ + no_timer_check = 1; + return 1; +} +__setup("no_timer_check", notimercheck); + /* * There is a nasty bug in some older SMP boards, their mptable lies * about the timer IRQ. We do the following to work around the situation: @@ -1938,10 +1947,13 @@ static void __init setup_ioapic_ids_from * - if this function detects that timer IRQs are defunct, then we fall * back to ISA timer IRQs */ -static int __init timer_irq_works(void) +int __init timer_irq_works(void) { unsigned long t1 = jiffies; + if (no_timer_check) + return 1; + local_irq_enable(); /* Let ten ticks pass... */ mdelay((10 * 1000) / HZ); @@ -2212,7 +2224,7 @@ int timer_uses_ioapic_pin_0; * is so screwy. Thanks to Brian Perkins for testing/hacking this beast * fanatically on his truly buggy board. */ -static inline void check_timer(void) +static inline void __init check_timer(void) { int apic1, pin1, apic2, pin2; int vector; diff -puN Documentation/kernel-parameters.txt~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option Documentation/kernel-parameters.txt --- a/Documentation/kernel-parameters.txt~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option +++ a/Documentation/kernel-parameters.txt @@ -599,8 +599,6 @@ and is between 256 and 4096 characters. hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages. - noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing - i8042.direct [HW] Put keyboard port into non-translated mode i8042.dumbkbd [HW] Pretend that controller can only read data from keyboard and cannot control its state @@ -1056,9 +1054,14 @@ and is between 256 and 4096 characters. in certain environments such as networked servers or real-time systems. + noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing + noirqdebug [IA-32] Disables the code which attempts to detect and disable unhandled interrupt sources. + no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for + broken timer IRQ sources. + noisapnp [ISAPNP] Disables ISA PnP code. noinitrd [RAM] Tells the kernel not to load any configured _ - 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/