From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH] KVM: x86: Avoid busy loops over uninjectable pending APIC timers Date: Thu, 21 Mar 2013 17:51:50 -0300 Message-ID: <20130321205150.GA17295@amt.cnet> References: <20130317104717.GA6117@redhat.com> <20130320193033.GB11138@amt.cnet> <20130320200319.GA16367@amt.cnet> <20130320213238.GB9382@redhat.com> <20130320231913.GA2319@amt.cnet> <20130321045446.GC9382@redhat.com> <20130321140224.GA29237@amt.cnet> <20130321141853.GU3889@redhat.com> <20130321162732.GF9382@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Zhang, Yang Z" , Jan Kiszka , kvm To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51312 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753086Ab3CUUv7 (ORCPT ); Thu, 21 Mar 2013 16:51:59 -0400 Content-Disposition: inline In-Reply-To: <20130321162732.GF9382@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: > > > But current PI patches do break them, thats my point. So we either > > > need to revise them again, or drop LAPIC timer reinjection. Making > > > apic_accept_irq semantics "it returns coalescing info, but only sometimes" > > > is dubious though. > > We may rollback to the initial idea: test both irr and pir to get coalescing info. In this case, inject LAPIC timer always in vcpu context. So apic_accept_irq() will return right coalescing info. > > Also, we need to add comments to tell caller, apic_accept_irq() can ensure the return value is correct only when caller is in target vcpu context. > > > We cannot touch irr while vcpu is in non-root operation, so we will have > to pass flag to apic_accept_irq() to let it know that it is called > synchronously. While all this is possible I want to know which guests > exactly will we break if we will not track interrupt coalescing for > lapic timer. If only 2.0 smp kernels will break we can probably drop it. RHEL4 / RHEL5 guests.