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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; Received: from SATLEXMB04.amd.com (165.204.84.17) by CO1NAM11FT018.mail.protection.outlook.com (10.13.175.16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.5186.14 via Frontend Transport; Wed, 20 Apr 2022 15:50:16 +0000 Received: from sp5-759chost.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 20 Apr 2022 10:50:14 -0500 From: Suravee Suthikulpanit To: , CC: , , , , , , , Suravee Suthikulpanit Subject: [PATCH 1/2] KVM: SVM: Use target APIC ID to complete AVIC IRQs when possible Date: Wed, 20 Apr 2022 10:49:53 -0500 Message-ID: <20220420154954.19305-2-suravee.suthikulpanit@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220420154954.19305-1-suravee.suthikulpanit@amd.com> References: <20220420154954.19305-1-suravee.suthikulpanit@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: a8453e13-92f3-43b6-b52f-08da22e57711 X-MS-TrafficTypeDiagnostic: DM5PR12MB1194:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Apr 2022 15:50:16.4975 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a8453e13-92f3-43b6-b52f-08da22e57711 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT018.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR12MB1194 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, an AVIC-enabled VM suffers from performance bottleneck when scaling to large number of vCPUs for I/O intensive workloads. In such case, a vCPU often executes halt instruction to get into idle state waiting for interrupts, in which KVM would de-schedule the vCPU from physical CPU. When AVIC HW tries to deliver interrupt to the halting vCPU, it would result in AVIC incomplete IPI #vmexit to notify KVM to reschedule the target vCPU into running state. Investigation has shown the main hotspot is in the kvm_apic_match_dest() in the following call stack where it tries to find target vCPUs corresponding to the information in the ICRH/ICRL registers. - handle_exit - svm_invoke_exit_handler - avic_incomplete_ipi_interception - kvm_apic_match_dest However, AVIC provides hints in the #vmexit info, which can be used to retrieve the destination guest physical APIC ID. In addition, since QEMU defines guest physical APIC ID to be the same as vCPU ID, it can be used to quickly identify the target vCPU to deliver IPI, and avoid the overhead from searching through all vCPUs to match the target vCPU. Reviewed-by: Maxim Levitsky Signed-off-by: Suravee Suthikulpanit --- arch/x86/kvm/svm/avic.c | 72 ++++++++++++++++++++++++++++++++++++++--- 1 file changed, 68 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 421619540ff9..c8b8a0cb02b0 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -285,11 +285,75 @@ void avic_ring_doorbell(struct kvm_vcpu *vcpu) put_cpu(); } -static void avic_kick_target_vcpus(struct kvm *kvm, struct kvm_lapic *source, - u32 icrl, u32 icrh) +/* + * A fast-path version of avic_kick_target_vcpus(), which attempts to match + * destination APIC ID to vCPU without looping through all vCPUs. + */ +static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source, + u32 icrl, u32 icrh, u32 index) { + u32 dest, apic_id; struct kvm_vcpu *vcpu; + int dest_mode = icrl & APIC_DEST_MASK; + int shorthand = icrl & APIC_SHORT_MASK; + struct kvm_svm *kvm_svm = to_kvm_svm(kvm); + u32 *avic_logical_id_table = page_address(kvm_svm->avic_logical_id_table_page); + + if (shorthand != APIC_DEST_NOSHORT) + return -EINVAL; + + /* + * The AVIC incomplete IPI #vmexit info provides index into + * the physical APIC ID table, which can be used to derive + * guest physical APIC ID. + */ + if (dest_mode == APIC_DEST_PHYSICAL) { + apic_id = index; + } else { + if (!apic_x2apic_mode(source)) { + /* For xAPIC logical mode, the index is for logical APIC table. */ + apic_id = avic_logical_id_table[index] & 0x1ff; + } else { + return -EINVAL; + } + } + + /* + * Assuming vcpu ID is the same as physical apic ID, + * and use it to retrieve the target vCPU. + */ + vcpu = kvm_get_vcpu_by_id(kvm, apic_id); + if (!vcpu) + return -EINVAL; + + if (apic_x2apic_mode(vcpu->arch.apic)) + dest = icrh; + else + dest = GET_APIC_DEST_FIELD(icrh); + + /* + * Try matching the destination APIC ID with the vCPU. + */ + if (kvm_apic_match_dest(vcpu, source, shorthand, dest, dest_mode)) { + vcpu->arch.apic->irr_pending = true; + svm_complete_interrupt_delivery(vcpu, + icrl & APIC_MODE_MASK, + icrl & APIC_INT_LEVELTRIG, + icrl & APIC_VECTOR_MASK); + return 0; + } + + return -EINVAL; +} + +static void avic_kick_target_vcpus(struct kvm *kvm, struct kvm_lapic *source, + u32 icrl, u32 icrh, u32 index) +{ unsigned long i; + struct kvm_vcpu *vcpu; + + if (!avic_kick_target_vcpus_fast(kvm, source, icrl, icrh, index)) + return; /* * Wake any target vCPUs that are blocking, i.e. waiting for a wake @@ -316,7 +380,7 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu) u32 icrh = svm->vmcb->control.exit_info_1 >> 32; u32 icrl = svm->vmcb->control.exit_info_1; u32 id = svm->vmcb->control.exit_info_2 >> 32; - u32 index = svm->vmcb->control.exit_info_2 & 0xFF; + u32 index = svm->vmcb->control.exit_info_2 & 0x1FF; struct kvm_lapic *apic = vcpu->arch.apic; trace_kvm_avic_incomplete_ipi(vcpu->vcpu_id, icrh, icrl, id, index); @@ -343,7 +407,7 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu) * set the appropriate IRR bits on the valid target * vcpus. So, we just need to kick the appropriate vcpu. */ - avic_kick_target_vcpus(vcpu->kvm, apic, icrl, icrh); + avic_kick_target_vcpus(vcpu->kvm, apic, icrl, icrh, index); break; case AVIC_IPI_FAILURE_INVALID_TARGET: break; -- 2.25.1