Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751218AbdFBQZD (ORCPT ); Fri, 2 Jun 2017 12:25:03 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:46604 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153AbdFBQZB (ORCPT ); Fri, 2 Jun 2017 12:25:01 -0400 Subject: Re: [PATCH] xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU To: Anoob Soman , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org References: <1496414988-12878-1-git-send-email-anoob.soman@citrix.com> Cc: jgross@suse.com From: Boris Ostrovsky Message-ID: <363cb97a-7dc1-ae4f-da93-30e7658cef00@oracle.com> Date: Fri, 2 Jun 2017 12:24:40 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1496414988-12878-1-git-send-email-anoob.soman@citrix.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1930 Lines: 67 > > static int set_affinity_irq(struct irq_data *data, const struct cpumask *dest, > bool force) > diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c > index 10f1ef5..1192f24 100644 > --- a/drivers/xen/evtchn.c > +++ b/drivers/xen/evtchn.c > @@ -58,6 +58,8 @@ > #include > #include > > +static DEFINE_PER_CPU(int, bind_last_selected_cpu); This should be moved into evtchn_bind_interdom_next_vcpu() since that's the only place referencing it. Why is it a percpu variable BTW? Wouldn't making it global result in better interrupt distribution? > + > struct per_user_data { > struct mutex bind_mutex; /* serialize bind/unbind operations */ > struct rb_root evtchns; > @@ -421,6 +423,36 @@ static void evtchn_unbind_from_user(struct per_user_data *u, > del_evtchn(u, evtchn); > } > > +static void evtchn_bind_interdom_next_vcpu(int evtchn) > +{ > + unsigned int selected_cpu, irq; > + struct irq_desc *desc = NULL; > + unsigned long flags; > + > + irq = irq_from_evtchn(evtchn); > + desc = irq_to_desc(irq); > + > + if (!desc) > + return; > + > + raw_spin_lock_irqsave(&desc->lock, flags); > + selected_cpu = this_cpu_read(bind_last_selected_cpu); > + selected_cpu = cpumask_next_and(selected_cpu, > + desc->irq_common_data.affinity, cpu_online_mask); > + > + if (unlikely(selected_cpu >= nr_cpu_ids)) > + selected_cpu = cpumask_first_and(desc->irq_common_data.affinity, > + cpu_online_mask); > + > + raw_spin_unlock_irqrestore(&desc->lock, flags); I think if you follow Juergen's suggestion of wrapping everything into irq_enable/disable you can drop the lock altogether (assuming you keep bind_last_selected_cpu percpu). -boris > + this_cpu_write(bind_last_selected_cpu, selected_cpu); > + > + local_irq_disable(); > + /* unmask expects irqs to be disabled */ > + xen_rebind_evtchn_to_cpu(evtchn, selected_cpu); > + local_irq_enable(); > +} > + >