Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751441AbbLUCBX (ORCPT ); Sun, 20 Dec 2015 21:01:23 -0500 Received: from mail-pf0-f181.google.com ([209.85.192.181]:36641 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751060AbbLUCBW (ORCPT ); Sun, 20 Dec 2015 21:01:22 -0500 Subject: Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts To: "Wu, Feng" , "pbonzini@redhat.com" , "rkrcmar@redhat.com" References: <1450229853-3886-1-git-send-email-feng.wu@intel.com> <1450229853-3886-3-git-send-email-feng.wu@intel.com> <56775ADB.10602@gmail.com> Cc: "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: Yang Zhang Message-ID: <56775D67.1030703@gmail.com> Date: Mon, 21 Dec 2015 10:01:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 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 Content-Length: 5578 Lines: 180 On 2015/12/21 9:55, 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: Monday, December 21, 2015 9:50 AM >> To: Wu, Feng ; pbonzini@redhat.com; >> rkrcmar@redhat.com >> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org >> Subject: Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d >> posted-interrupts >> >> On 2015/12/16 9:37, Feng Wu wrote: >>> Use vector-hashing to deliver lowest-priority interrupts for >>> VT-d posted-interrupts. >>> >>> Signed-off-by: Feng Wu >>> --- >>> arch/x86/kvm/lapic.c | 67 >> ++++++++++++++++++++++++++++++++++++++++++++++++++++ >>> arch/x86/kvm/lapic.h | 2 ++ >>> arch/x86/kvm/vmx.c | 12 ++++++++-- >>> 3 files changed, 79 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >>> index e29001f..d4f2c8f 100644 >>> --- a/arch/x86/kvm/lapic.c >>> +++ b/arch/x86/kvm/lapic.c >>> @@ -854,6 +854,73 @@ out: >>> } >>> >>> /* >>> + * This routine handles lowest-priority interrupts using vector-hashing >>> + * mechanism. As an example, modern Intel CPUs use this method to handle >>> + * lowest-priority interrupts. >>> + * >>> + * Here is the details about the vector-hashing mechanism: >>> + * 1. For lowest-priority interrupts, store all the possible destination >>> + * vCPUs in an array. >>> + * 2. Use "guest vector % max number of destination vCPUs" to find the right >>> + * destination vCPU in the array for the lowest-priority interrupt. >>> + */ >>> +struct kvm_vcpu *kvm_intr_vector_hashing_dest(struct kvm *kvm, >>> + struct kvm_lapic_irq *irq) >>> +{ >>> + struct kvm_apic_map *map; >>> + struct kvm_vcpu *vcpu = NULL; >>> + >>> + if (irq->shorthand) >>> + return NULL; >>> + >>> + rcu_read_lock(); >>> + map = rcu_dereference(kvm->arch.apic_map); >>> + >>> + if (!map) >>> + goto out; >>> + >>> + if ((irq->dest_mode != APIC_DEST_PHYSICAL) && >>> + kvm_lowest_prio_delivery(irq)) { >>> + u16 cid; >>> + int i, idx = 0; >>> + unsigned long bitmap = 1; >>> + unsigned int dest_vcpus = 0; >>> + struct kvm_lapic **dst = NULL; >>> + >>> + >>> + if (!kvm_apic_logical_map_valid(map)) >>> + goto out; >>> + >>> + apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap); >>> + >>> + if (cid >= ARRAY_SIZE(map->logical_map)) >>> + goto out; >>> + >>> + dst = map->logical_map[cid]; >>> + >>> + for_each_set_bit(i, &bitmap, 16) { >>> + if (!dst[i] && !kvm_lapic_enabled(dst[i]->vcpu)) { >>> + clear_bit(i, &bitmap); >>> + continue; >>> + } >>> + } >>> + >>> + dest_vcpus = hweight16(bitmap); >>> + >>> + if (dest_vcpus != 0) { >>> + idx = kvm_vector_2_index(irq->vector, dest_vcpus, >>> + &bitmap, 16); >>> + vcpu = dst[idx-1]->vcpu; >>> + } >>> + } >>> + >>> +out: >>> + rcu_read_unlock(); >>> + return vcpu; >>> +} >>> +EXPORT_SYMBOL_GPL(kvm_intr_vector_hashing_dest); >>> + >>> +/* >>> * Add a pending IRQ into lapic. >>> * Return 1 if successfully added and 0 if discarded. >>> */ >>> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h >>> index 6890ef0..52bffce 100644 >>> --- a/arch/x86/kvm/lapic.h >>> +++ b/arch/x86/kvm/lapic.h >>> @@ -172,4 +172,6 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, >> struct kvm_lapic_irq *irq, >>> struct kvm_vcpu **dest_vcpu); >>> int kvm_vector_2_index(u32 vector, u32 dest_vcpus, >>> const unsigned long *bitmap, u32 bitmap_size); >>> +struct kvm_vcpu *kvm_intr_vector_hashing_dest(struct kvm *kvm, >>> + struct kvm_lapic_irq *irq); >>> #endif >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index 5eb56ed..3f89189 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -10702,8 +10702,16 @@ static int vmx_update_pi_irte(struct kvm *kvm, >> unsigned int host_irq, >>> */ >>> >>> kvm_set_msi_irq(e, &irq); >>> - if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) >>> - continue; >>> + >>> + if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) { >>> + if (!kvm_vector_hashing_enabled() || >>> + irq.delivery_mode != >> APIC_DM_LOWEST) >>> + continue; >>> + >>> + vcpu = kvm_intr_vector_hashing_dest(kvm, &irq); >>> + if (!vcpu) >>> + continue; >>> + } >> >> I am a little confused with the 'continue'. If the destination is not >> single vcpu, shouldn't we rollback to use non-PI mode? > > Here is the logic: > - If it is single destination, we will use PI no matter it is fixed or lowest-priority. > - If it is not single destination: > a) It is fixed, we will use non-PI > b) It is lowest-priority and vector-hashing is enabled, we will use PI > c) otherwise, use non-PI If it is single destination previously, then change to no-single mode. Can current code cover this case? > > Thanks, > Feng > >> >>> >>> vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu)); >>> vcpu_info.vector = irq.vector; >>> >> >> >> -- >> best regards >> yang >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ -- best regards yang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/