From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220AbcGAIYb (ORCPT ); Fri, 1 Jul 2016 04:24:31 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:36092 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbcGAIY1 (ORCPT ); Fri, 1 Jul 2016 04:24:27 -0400 Subject: Re: [PATCH v1 10/11] KVM: x86: add KVM_CAP_X2APIC_API To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20160630205429.16480-1-rkrcmar@redhat.com> <20160630205429.16480-11-rkrcmar@redhat.com> Cc: "Lan, Tianyu" , Igor Mammedov , Jan Kiszka , Peter Xu From: Paolo Bonzini Message-ID: Date: Fri, 1 Jul 2016 10:24:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <20160630205429.16480-11-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/06/2016 22:54, Radim Krčmář wrote: > KVM_CAP_X2APIC_API can be enabled to extend APIC ID in get/set ioctl and MSI > addresses to 32 bits. Both are needed to support x2APIC. > > The capability has to be toggleable and disabled by default, because get/set > ioctl shifted and truncated APIC ID to 8 bits by using a non-standard protocol > inspired by xAPIC and the change is not backward-compatible. > > Changes to MSI addresses follow the format used by interrupt remapping unit. > The upper address word, that used to be 0, contains upper 24 bits of the LAPIC > address in its upper 24 bits. Lower 8 bits are reserved as 0. > Using the upper address word is not backward-compatible either as we didn't > check that userspace zeroed the word. Reserved bits are still not explicitly > checked, but non-zero data will affect LAPIC addresses, which will cause a bug. > > Signed-off-by: Radim Krčmář > --- > v1: > * rewritten with a toggleable capability [Paolo] > * dropped MSI_ADDR_EXT_DEST_ID to enforce reserved bits > > Documentation/virtual/kvm/api.txt | 26 ++++++++++++++++++++++++++ > arch/x86/include/asm/kvm_host.h | 4 +++- > arch/x86/kvm/irq_comm.c | 14 ++++++++++---- > arch/x86/kvm/lapic.c | 2 +- > arch/x86/kvm/vmx.c | 2 +- > arch/x86/kvm/x86.c | 12 ++++++++++++ > include/uapi/linux/kvm.h | 1 + > 7 files changed, 54 insertions(+), 7 deletions(-) > > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > index 09efa9eb3926..0f978089a0f6 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -1482,6 +1482,9 @@ struct kvm_irq_routing_msi { > __u32 pad; > }; > > +If KVM_CAP_X2APIC_API is enabled, then address_hi bits 31-8 contain bits 31-8 > +of destination id and address_hi bits 7-0 is must be 0. On x86, address_hi is ignored unless the KVM_CAP_X2APIC_API capability is enabled. If it is enabled, address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of address_hi must be zero. > struct kvm_irq_routing_s390_adapter { > __u64 ind_addr; > __u64 summary_addr; > @@ -1583,6 +1586,13 @@ struct kvm_lapic_state { > Reads the Local APIC registers and copies them into the input argument. The > data format and layout are the same as documented in the architecture manual. > > +If KVM_CAP_X2APIC_API is enabled, then the format of APIC_ID register depends > +on APIC mode (reported by MSR_IA32_APICBASE) of its VCPU. The format follows > +xAPIC otherwise. > + > +x2APIC stores APIC ID as little endian in bits 31-0 of APIC_ID register. > +xAPIC stores bits 7-0 of APIC ID in register bits 31-24. If KVM_CAP_X2APIC_API is enabled, then the format of APIC_ID register depends on the APIC mode (reported by MSR_IA32_APICBASE) of its VCPU. x2APIC stores APIC ID in the APIC_ID register (bytes 32-35). xAPIC only allows an 8-bit APIC ID which is stored in bits 31-24 of the APIC register, or equivalently in byte 35 of struct kvm_lapic_state's regs field. If KVM_CAP_X2APIC_API is disabled, struct kvm_lapic_state always uses xAPIC format. > + > > 4.58 KVM_SET_LAPIC > > @@ -1600,6 +1610,8 @@ struct kvm_lapic_state { > Copies the input argument into the Local APIC registers. The data format > and layout are the same as documented in the architecture manual. > > +See the note about APIC_ID register in KVM_GET_LAPIC. The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's regs field) depends on the state of the KVM_CAP_X2APIC_API capability. See the note in KVM_GET_LAPIC. > > 4.59 KVM_IOEVENTFD > > @@ -2180,6 +2192,9 @@ struct kvm_msi { > > No flags are defined so far. The corresponding field must be 0. > > +If KVM_CAP_X2APIC_API is enabled, then address_hi bits 31-8 contain bits 31-8 > +of destination id and address_hi bits 7-0 is must be 0. Please use the same wording as in KVM_SET_GSI_ROUTING. > > 4.71 KVM_CREATE_PIT2 > > @@ -3811,6 +3826,17 @@ Allows use of runtime-instrumentation introduced with zEC12 processor. > Will return -EINVAL if the machine does not support runtime-instrumentation. > Will return -EBUSY if a VCPU has already been created. > > +7.7 KVM_CAP_X2APIC_API > + > +Architectures: x86 > +Parameters: none > +Returns: 0 on success, -EINVAL if reserved parameters are not 0 > + > +Enabling this capability changes the behavior of KVM_SET_GSI_ROUTING, > +KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC ... ", allowing the use of 32-bit APIC IDs". > . See KVM_CAP_X2APIC_API > +in their respective sections. > + > + > 8. Other capabilities. > ---------------------- > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 459a789cb3da..48b0ca18066c 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -782,6 +782,8 @@ struct kvm_arch { > u32 ldr_mode; > struct page *avic_logical_id_table_page; > struct page *avic_physical_id_table_page; > + > + bool x2apic_api; > }; > > struct kvm_vm_stat { > @@ -1365,7 +1367,7 @@ bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq, > struct kvm_vcpu **dest_vcpu); > > void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e, > - struct kvm_lapic_irq *irq); > + struct kvm_lapic_irq *irq, bool x2apic_api); Just pass a struct kvm as the first argument. > > static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) > { > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c > index 47ad681a33fd..4594644ab090 100644 > --- a/arch/x86/kvm/irq_comm.c > +++ b/arch/x86/kvm/irq_comm.c > @@ -111,12 +111,17 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > } > > void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e, > - struct kvm_lapic_irq *irq) > + struct kvm_lapic_irq *irq, bool x2apic_api) > { > trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data); > > irq->dest_id = (e->msi.address_lo & > MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT; > + if (x2apic_api) > + /* MSI_ADDR_EXT_DEST_ID() is omitted to introduce bugs on > + * userspaces that set reserved bits 0-7. > + */ Reread Rusty's API design guidelines and come back. ;) Seriously, please validate the address_hi at both places (KVM_SET_GSI_ROUTING and KVM_SIGNAL_MSI) and WARN here if you get non-zero bits 7-0. > + irq->dest_id |= e->msi.address_hi; > irq->vector = (e->msi.data & > MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT; > irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo; > @@ -137,7 +142,7 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e, > if (!level) > return -1; > > - kvm_set_msi_irq(e, &irq); > + kvm_set_msi_irq(e, &irq, kvm->arch.x2apic_api); > > return kvm_irq_delivery_to_apic(kvm, NULL, &irq, NULL); > } > @@ -153,7 +158,7 @@ int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e, > if (unlikely(e->type != KVM_IRQ_ROUTING_MSI)) > return -EWOULDBLOCK; > > - kvm_set_msi_irq(e, &irq); > + kvm_set_msi_irq(e, &irq, kvm->arch.x2apic_api); > > if (kvm_irq_delivery_to_apic_fast(kvm, NULL, &irq, &r, NULL)) > return r; > @@ -393,7 +398,8 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu, > if (entry->type != KVM_IRQ_ROUTING_MSI) > continue; > > - kvm_set_msi_irq(entry, &irq); > + kvm_set_msi_irq(entry, &irq, > + vcpu->kvm->arch.x2apic_api); > > if (irq.level && kvm_apic_match_dest(vcpu, NULL, 0, > irq.dest_id, irq.dest_mode)) > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 46eb71c425cf..178605635df5 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1983,7 +1983,7 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu) > static void __kvm_apic_state_fixup(struct kvm_vcpu *vcpu, > struct kvm_lapic_state *s, bool set) > { > - if (apic_x2apic_mode(vcpu->arch.apic)) { > + if (apic_x2apic_mode(vcpu->arch.apic) && !vcpu->kvm->arch.x2apic_api) { > u32 *id = (u32 *)(s->regs + APIC_ID); > if (set) > *id >>= 24; > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index a10038258b80..ea1f439b444e 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -11075,7 +11075,7 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq, > * We will support full lowest-priority interrupt later. > */ > > - kvm_set_msi_irq(e, &irq); > + kvm_set_msi_irq(e, &irq, kvm->arch.x2apic_api); > if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) { > /* > * Make sure the IRTE is in remapped mode if > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 043f110f2210..16b55f09dd16 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2576,6 +2576,7 @@ 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_X2APIC_API: > #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT > case KVM_CAP_ASSIGN_DEV_IRQ: > case KVM_CAP_PCI_2_3: > @@ -3799,6 +3800,17 @@ split_irqchip_unlock: > mutex_unlock(&kvm->lock); > break; > } > + case KVM_CAP_X2APIC_API: { > + struct kvm_enable_cap valid = {.cap = KVM_CAP_X2APIC_API}; > + > + r = -EINVAL; > + if (memcmp(cap, &valid, sizeof(valid))) > + break; Nice trick, and strict argument checking in general is a good idea. However it's ugly to do it only for KVM_CAP_X2APIC_API and we've really bad at strict argument checking elsewhere. For consistency, please check that args[0] is zero, and forgo other violations. :( Paolo > + kvm->arch.x2apic_api = true; > + r = 0; > + break; > + } > default: > r = -EINVAL; > break; > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 05ebf475104c..43b355d6db7b 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -866,6 +866,7 @@ struct kvm_ppc_smmu_info { > #define KVM_CAP_ARM_PMU_V3 126 > #define KVM_CAP_VCPU_ATTRIBUTES 127 > #define KVM_CAP_MAX_VCPU_ID 128 > +#define KVM_CAP_X2APIC_API 129 > > #ifdef KVM_CAP_IRQ_ROUTING > >