From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1428295AbdDXS70 (ORCPT ); Mon, 24 Apr 2017 14:59:26 -0400 Received: from mail-wm0-f54.google.com ([74.125.82.54]:36139 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1428210AbdDXS7O (ORCPT ); Mon, 24 Apr 2017 14:59:14 -0400 Date: Mon, 24 Apr 2017 20:59:09 +0200 From: Daniel Lezcano To: Marc Zyngier Cc: tglx@linutronix.de, Mark Rutland , Vineet Gupta , Patrice Chotard , Kukjin Kim , Krzysztof Kozlowski , Javier Martinez Canillas , Christoffer Dall , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, kernel@stlinux.com, linux-samsung-soc@vger.kernel.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Subject: Re: [PATCH V9 1/3] irq: Allow to pass the IRQF_TIMER flag with percpu irq request Message-ID: <20170424185909.GD2137@mai> References: <1493042494-14057-1-git-send-email-daniel.lezcano@linaro.org> <398f3f3d-c567-0f1f-1a43-9b8d5805d5fd@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <398f3f3d-c567-0f1f-1a43-9b8d5805d5fd@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 24, 2017 at 07:46:43PM +0100, Marc Zyngier wrote: > On 24/04/17 15:01, Daniel Lezcano wrote: > > In the next changes, we track when the interrupts occur in order to > > statistically compute when is supposed to happen the next interrupt. > > > > In all the interruptions, it does not make sense to store the timer interrupt > > occurences and try to predict the next interrupt as when know the expiration > > time. > > > > The request_irq() has a irq flags parameter and the timer drivers use it to > > pass the IRQF_TIMER flag, letting us know the interrupt is coming from a timer. > > Based on this flag, we can discard these interrupts when tracking them. > > > > But, the API request_percpu_irq does not allow to pass a flag, hence specifying > > if the interrupt type is a timer. > > > > Add a function request_percpu_irq_flags() where we can specify the flags. The > > request_percpu_irq() function is changed to be a wrapper to > > request_percpu_irq_flags() passing a zero flag parameter. > > > > Change the timers using request_percpu_irq() to use request_percpu_irq_flags() > > instead with the IRQF_TIMER flag set. > > > > For now, in order to prevent a misusage of this parameter, only the IRQF_TIMER > > flag (or zero) is a valid parameter to be passed to the > > request_percpu_irq_flags() function. > > [...] > > > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > > index 35d7100..602e0a8 100644 > > --- a/virt/kvm/arm/arch_timer.c > > +++ b/virt/kvm/arm/arch_timer.c > > @@ -523,8 +523,9 @@ int kvm_timer_hyp_init(void) > > host_vtimer_irq_flags = IRQF_TRIGGER_LOW; > > } > > > > - err = request_percpu_irq(host_vtimer_irq, kvm_arch_timer_handler, > > - "kvm guest timer", kvm_get_running_vcpus()); > > + err = request_percpu_irq_flags(host_vtimer_irq, kvm_arch_timer_handler, > > + IRQF_TIMER, "kvm guest timer", > > + kvm_get_running_vcpus()); > > if (err) { > > kvm_err("kvm_arch_timer: can't request interrupt %d (%d)\n", > > host_vtimer_irq, err); > > > > How is that useful? This timer is controlled by the guest OS, and not > the host kernel. Can you explain how you intend to make use of that > information in this case? Isn't it a source of interruption on the host kernel? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog