From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751822AbcAUFm5 (ORCPT ); Thu, 21 Jan 2016 00:42:57 -0500 Received: from mail-pa0-f67.google.com ([209.85.220.67]:35066 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750792AbcAUFmz (ORCPT ); Thu, 21 Jan 2016 00:42:55 -0500 Subject: Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts To: "Wu, Feng" , "pbonzini@redhat.com" , "rkrcmar@redhat.com" References: <1453254177-103002-1-git-send-email-feng.wu@intel.com> <1453254177-103002-3-git-send-email-feng.wu@intel.com> <56A06B60.5030501@gmail.com> Cc: "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" From: Yang Zhang Message-ID: <56A06FD7.4050803@gmail.com> Date: Thu, 21 Jan 2016 13:42:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/1/21 13:33, Wu, Feng wrote: > > >> -----Original Message----- >> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- >> owner@vger.kernel.org] On Behalf Of Yang Zhang >> Sent: Thursday, January 21, 2016 1:24 PM >> To: Wu, Feng ; pbonzini@redhat.com; >> rkrcmar@redhat.com >> Cc: linux-kernel@vger.kernel.org; kvm@vger.kernel.org >> Subject: Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest- >> priority interrupts >> >> On 2016/1/20 9:42, Feng Wu wrote: >>> Use vector-hashing to deliver lowest-priority interrupts, As an >>> example, modern Intel CPUs in server platform use this method to >>> handle lowest-priority interrupts. >>> >>> Signed-off-by: Feng Wu >>> --- >>> bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic >> *src, >>> struct kvm_lapic_irq *irq, int *r, unsigned long *dest_map) >>> { >>> @@ -727,21 +743,51 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm >> *kvm, struct kvm_lapic *src, >>> >>> dst = map->logical_map[cid]; >>> >>> - if (kvm_lowest_prio_delivery(irq)) { >>> + if (!kvm_lowest_prio_delivery(irq)) >>> + goto set_irq; >>> + >>> + if (!kvm_vector_hashing_enabled()) { >>> int l = -1; >>> for_each_set_bit(i, &bitmap, 16) { >>> if (!dst[i]) >>> continue; >>> if (l < 0) >>> l = i; >>> - else if (kvm_apic_compare_prio(dst[i]->vcpu, >> dst[l]->vcpu) < 0) >>> + else if (kvm_apic_compare_prio(dst[i]->vcpu, >>> + dst[l]->vcpu) < 0) >>> l = i; >>> } >>> - >>> bitmap = (l >= 0) ? 1 << l : 0; >>> + } else { >>> + int idx = 0; >>> + unsigned int dest_vcpus = 0; >>> + >>> + dest_vcpus = hweight16(bitmap); >>> + if (dest_vcpus == 0) >>> + goto out; >>> + >>> + idx = kvm_vector_2_index(irq->vector, >>> + dest_vcpus, &bitmap, 16); >>> + >>> + /* >>> + * We may find a hardware disabled LAPIC here, if >> that >>> + * is the case, print out a error message once for each >>> + * guest and return. >>> + */ >>> + if (!dst[idx-1] && >>> + (kvm->arch.disabled_lapic_found == 0)) { >>> + kvm->arch.disabled_lapic_found = 1; >>> + printk(KERN_ERR >>> + "Disabled LAPIC found during irq >> injection\n"); >>> + goto out; >> >> What does "goto out" mean? Inject successfully or fail? According the >> value of ret which is set to ture here, it means inject successfully but >> i = -1. >> > > Oh, I didn't notice 'ret' is initialized to true, I thought it was initialized > to false like another function, I should add a "ret = false' here. We should > failed to inject the interrupt since hardware disabled LAPIC is found. I remember we have discussed that even the LAPIC is software disabled, it still can respond to some interrupts like INIT, NMI, SMI, and SIPI messages. Isn't current logic still problematically? -- best regards yang