Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758997AbcLBTpA (ORCPT ); Fri, 2 Dec 2016 14:45:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50340 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758793AbcLBTor (ORCPT ); Fri, 2 Dec 2016 14:44:47 -0500 From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Igor Mammedov Subject: [PATCH 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff Date: Fri, 2 Dec 2016 20:44:01 +0100 Message-Id: <20161202194401.10038-5-rkrcmar@redhat.com> In-Reply-To: <20161202194401.10038-1-rkrcmar@redhat.com> References: <20161202194401.10038-1-rkrcmar@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 02 Dec 2016 19:44:47 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2963 Lines: 81 LAPIC after reset is in xAPIC mode, which poses a problem for hotplug of VCPUs with high APIC ID, because reset VCPU is waiting for INIT/SIPI, but there is no way to uniquely address it using xAPIC. >From many possible options, we chose the one that also works on real hardware: accepting interrupts addressed to LAPIC's x2APIC ID even in xAPIC mode. KVM intentionally differs from real hardware, because real hardware (Knights Landing) does just "x2apic_id & 0xff" to decide whether to accept the interrupt in xAPIC mode and it can deliver one interrupt to more than one physical destination, e.g. 0x123 to 0x123 and 0x23. Add a capability to let userspace know that we do something now. Signed-off-by: Radim Krčmář --- arch/x86/kvm/lapic.c | 13 +++++++++++-- arch/x86/kvm/x86.c | 1 + include/uapi/linux/kvm.h | 1 + 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 42edf1ea2909..b85985985ac8 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -199,10 +199,15 @@ static void recalculate_apic_map(struct kvm *kvm) xapic_id = kvm_xapic_id(apic); x2apic_id = kvm_x2apic_id(apic); - if (apic_x2apic_mode(apic) && + /* Hotplug hack: see kvm_apic_match_physical_addr(), ... */ + if ((apic_x2apic_mode(apic) || x2apic_id > 0xff) && x2apic_id <= new->max_apic_id) new->phys_map[x2apic_id] = apic; - else if (!apic_x2apic_mode(apic)) + /* + * ... xAPIC ID of VCPUs with APIC ID > 0xff will wrap-around, + * prevent them from masking VCPUs with APIC ID <= 0xff. + */ + if (!apic_x2apic_mode(apic) && !new->phys_map[xapic_id]) new->phys_map[xapic_id] = apic; ldr = kvm_lapic_get_reg(apic, APIC_LDR); @@ -612,6 +617,10 @@ static bool kvm_apic_match_physical_addr(struct kvm_lapic *apic, u32 mda) if (apic_x2apic_mode(apic)) return mda == kvm_x2apic_id(apic); + /* Hotplug hack: LAPIC in xAPIC mode also accepts x2APIC. */ + if (kvm_x2apic_id(apic) > 0xff && mda == kvm_x2apic_id(apic)) + return true; + return mda == kvm_xapic_id(apic); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7770d77c828d..945e8eeb4eb1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2618,6 +2618,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_DISABLE_QUIRKS: case KVM_CAP_SET_BOOT_CPU_ID: case KVM_CAP_SPLIT_IRQCHIP: + case KVM_CAP_X86_ALWAYS_ACCEPT_X2APIC_DEST: #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT case KVM_CAP_ASSIGN_DEV_IRQ: case KVM_CAP_PCI_2_3: diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index e9f5ceffd741..f25efa375255 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -871,6 +871,7 @@ struct kvm_ppc_smmu_info { #define KVM_CAP_S390_USER_INSTR0 130 #define KVM_CAP_MSI_DEVID 131 #define KVM_CAP_PPC_HTM 132 +#define KVM_CAP_X86_ALWAYS_ACCEPT_X2APIC_DEST 133 #ifdef KVM_CAP_IRQ_ROUTING -- 2.10.2