From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752887AbbFEV7i (ORCPT ); Fri, 5 Jun 2015 17:59:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46432 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752242AbbFEV7f (ORCPT ); Fri, 5 Jun 2015 17:59:35 -0400 Date: Fri, 5 Jun 2015 18:59:15 -0300 From: Marcelo Tosatti To: "Wu, Feng" Cc: "hpa@zytor.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "x86@kernel.org" , "gleb@kernel.org" , "pbonzini@redhat.com" , "dwmw2@infradead.org" , "joro@8bytes.org" , "alex.williamson@redhat.com" , "jiang.liu@linux.intel.com" , "eric.auger@linaro.org" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked Message-ID: <20150605215915.GA1382@amt.cnet> References: <20150304120608.GA26762@amt.cnet> <20150312011526.GA5878@amt.cnet> <20150325231738.GA7333@amt.cnet> <20150327193013.GA6502@amt.cnet> <20150330235533.GA15792@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 14, 2015 at 07:37:44AM +0000, Wu, Feng wrote: > > > > -----Original Message----- > > From: Marcelo Tosatti [mailto:mtosatti@redhat.com] > > Sent: Tuesday, March 31, 2015 7:56 AM > > To: Wu, Feng > > Cc: hpa@zytor.com; tglx@linutronix.de; mingo@redhat.com; x86@kernel.org; > > gleb@kernel.org; pbonzini@redhat.com; dwmw2@infradead.org; > > joro@8bytes.org; alex.williamson@redhat.com; jiang.liu@linux.intel.com; > > eric.auger@linaro.org; linux-kernel@vger.kernel.org; > > iommu@lists.linux-foundation.org; kvm@vger.kernel.org > > Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU > > is blocked > > > > On Mon, Mar 30, 2015 at 04:46:55AM +0000, Wu, Feng wrote: > > > > > > > > > > -----Original Message----- > > > > From: Marcelo Tosatti [mailto:mtosatti@redhat.com] > > > > Sent: Saturday, March 28, 2015 3:30 AM > > > > To: Wu, Feng > > > > Cc: hpa@zytor.com; tglx@linutronix.de; mingo@redhat.com; > > x86@kernel.org; > > > > gleb@kernel.org; pbonzini@redhat.com; dwmw2@infradead.org; > > > > joro@8bytes.org; alex.williamson@redhat.com; jiang.liu@linux.intel.com; > > > > eric.auger@linaro.org; linux-kernel@vger.kernel.org; > > > > iommu@lists.linux-foundation.org; kvm@vger.kernel.org > > > > Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when > > vCPU > > > > is blocked > > > > > > > > On Fri, Mar 27, 2015 at 06:34:14AM +0000, Wu, Feng wrote: > > > > > > > Currently, the following code is executed before local_irq_disable() is > > > > called, > > > > > > > so do you mean 1)moving local_irq_disable() to the place before it. 2) > > after > > > > > > interrupt > > > > > > > is disabled, set KVM_REQ_EVENT in case the ON bit is set? > > > > > > > > > > > > 2) after interrupt is disabled, set KVM_REQ_EVENT in case the ON bit > > > > > > is set. > > > > > > > > > > Here is my understanding about your comments here: > > > > > - Disable interrupts > > > > > - Check 'ON' > > > > > - Set KVM_REQ_EVENT if 'ON' is set > > > > > > > > > > Then we can put the above code inside " if > > > > (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) " > > > > > just like it used to be. However, I still have some questions about this > > > > comment: > > > > > > > > > > 1. Where should I set KVM_REQ_EVENT? In function vcpu_enter_guest(), > > or > > > > other places? > > > > > > > > See below: > > > > > > > > > If in vcpu_enter_guest(), since currently local_irq_disable() is called after > > > > 'KVM_REQ_EVENT' > > > > > is checked, is it helpful to set KVM_REQ_EVENT after local_irq_disable() is > > > > called? > > > > > > > > local_irq_disable(); > > > > > > > > *** add code here *** > > > > > > So we need add code like the following here, right? > > > > > > if ('ON' is set) > > > kvm_make_request(KVM_REQ_EVENT, vcpu); > > > > Hi Marcelo, > > I changed the code as above, then I found that the ping latency was extremely big, (70ms - 400ms). > I digged into it and got the root cause. We cannot use "checking-on" as the judgment, since 'ON' > can be cleared by hypervisor software in lots of places. In this case, KVM_REQ_EVENT cannot be > set when we check 'ON' bit, hence the interrupts are not injected to the guest in time. > > Please refer to the following code, in which 'ON' bit can be cleared: > > apic_find_highest_irr () --> vmx_sync_pir_to_irr () --> pi_test_and_clear_on() > > Searching from the code step by step, apic_find_highest_irr() can be called by many other guys. > > Thanks, Ok then, ignore my suggestion. Can you resend the latest version please ?