Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758671AbbLBO4J (ORCPT ); Wed, 2 Dec 2015 09:56:09 -0500 Received: from smtp.citrix.com ([66.165.176.89]:35094 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758639AbbLBO4H (ORCPT ); Wed, 2 Dec 2015 09:56:07 -0500 X-IronPort-AV: E=Sophos;i="5.20,373,1444694400"; d="scan'208";a="315971724" Message-ID: <565F0666.9030602@citrix.com> Date: Wed, 2 Dec 2015 14:55:34 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Sander Eikelenboom , , CC: , Subject: Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. References: <80dcf47eb772c65a62652d7a56c8ed26@eikelenboom.it> In-Reply-To: <80dcf47eb772c65a62652d7a56c8ed26@eikelenboom.it> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2369 Lines: 79 On 28/11/15 15:47, Sander Eikelenboom wrote: > genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 (rtc0) We shouldn't register an rtc_cmos device because its legacy irq conflicts with the irq needed for hvc0. For a multi VCPU guest irq 8 is in use for the pv spinlocks and this gets requested first, preventing the rtc device from probing. Does this patch fix it for you? David 8<-------------------- x86: rtc_cmos platform device requires legacy irqs Adding the rtc platform device when there are no legacy irqs (no legacy PIC) causes a conflict with other devices that end up using the same irq number. In a single VCPU PV guest we should have: /proc/interrupts: CPU0 0: 4934 xen-percpu-virq timer0 1: 0 xen-percpu-ipi spinlock0 2: 0 xen-percpu-ipi resched0 3: 0 xen-percpu-ipi callfunc0 4: 0 xen-percpu-virq debug0 5: 0 xen-percpu-ipi callfuncsingle0 6: 0 xen-percpu-ipi irqwork0 7: 321 xen-dyn-event xenbus 8: 90 xen-dyn-event hvc_console ... But hvc_console cannot get its interrupt because it is already in use by rtc0 and the console does not work. genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 (rtc0) The rtc_cmos device requires a particular legacy irq so don't add it if there are no legacy irqs. Signed-off-by: David Vrabel --- arch/x86/kernel/rtc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c index cd96852..07c70f1 100644 --- a/arch/x86/kernel/rtc.c +++ b/arch/x86/kernel/rtc.c @@ -14,6 +14,7 @@ #include #include #include +#include #ifdef CONFIG_X86_32 /* @@ -200,6 +201,10 @@ static __init int add_rtc_cmos(void) } #endif + /* RTC uses legacy IRQs. */ + if (!nr_legacy_irqs()) + return -ENODEV; + platform_device_register(&rtc_device); dev_info(&rtc_device.dev, "registered platform RTC device (no PNP device found)\n"); -- 2.1.4 -- 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/