Re: [PATCH v2 11/13] KVM: x86: add KVM_CAP_X2APIC_API

Yang Zhang
2016-07-11T06:06:56Z

On 2016/7/8 1:15, 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

Does this means we cannot migrate the VM from KVM_CAP_X2APIC_API enabled
host to the disable host even VM doesn't have more than 255 VCPUs?

> checked, but non-zero data will affect LAPIC addresses, which will cause a bug.
>
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
> v2:
> * pass struct kvm into kvm_set_msi_irq [Paolo]
> * trace address_hi [David]
> * use hex dst, like other tracepoins
> * strict reserved MSI bits checking [Paolo]
> * loose reserved capability bits checking [Paolo]
> * improved documentation [Paolo]
>
> Documentation/virtual/kvm/api.txt | 32 ++++++++++++++++++++++++++++++++
> arch/x86/include/asm/kvm_host.h | 4 +++-
> arch/x86/kvm/irq_comm.c | 26 +++++++++++++++++++++-----
> arch/x86/kvm/lapic.c | 13 +++++++++----
> arch/x86/kvm/vmx.c | 2 +-
> arch/x86/kvm/x86.c | 5 +++++
> include/trace/events/kvm.h | 5 +++--
> include/uapi/linux/kvm.h | 1 +
> 8 files changed, 75 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 09efa9eb3926..a8f2ef910f98 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1482,6 +1482,10 @@ struct kvm_irq_routing_msi {
> __u32 pad;
> };
>
> +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 +1587,15 @@ 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 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 +1613,10 @@ 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.
>
> +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 +2197,10 @@ struct kvm_msi {
>
> No flags are defined so far. The corresponding field 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.
> +
>
> 4.71 KVM_CREATE_PIT2
>
> @@ -3811,6 +3832,17 @@ 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
> +
> +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 643e3dffcd85..f1b202b34c72 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 {
> @@ -1364,7 +1366,7 @@ bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
> 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,
> +void kvm_set_msi_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
> struct kvm_lapic_irq *irq);
>
> 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 889563d50c55..2ff9691e4603 100644
> --- a/arch/x86/kvm/irq_comm.c
> +++ b/arch/x86/kvm/irq_comm.c
> @@ -110,13 +110,17 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> return r;
> }
>
> -void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
> +void kvm_set_msi_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
> struct kvm_lapic_irq *irq)
> {
> - trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);
> + trace_kvm_msi_set_irq(e->msi.address_lo | (kvm->arch.x2apic_api ?
> + (u64)e->msi.address_hi << 32 : 0),
> + e->msi.data);
>
> irq->dest_id = (e->msi.address_lo &
> MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
> + if (kvm->arch.x2apic_api)
> + irq->dest_id |= MSI_ADDR_EXT_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;
> @@ -129,15 +133,24 @@ void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
> }
> EXPORT_SYMBOL_GPL(kvm_set_msi_irq);
>
> +static inline bool kvm_msi_route_invalid(struct kvm *kvm,
> + struct kvm_kernel_irq_routing_entry *e)
> +{
> + return kvm->arch.x2apic_api && (e->msi.address_hi & 0xff);
> +}
> +
> int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> struct kvm *kvm, int irq_source_id, int level, bool line_status)
> {
> struct kvm_lapic_irq irq;
>
> + if (kvm_msi_route_invalid(kvm, e))
> + return -EINVAL;
> +
> if (!level)
> return -1;
>
> - kvm_set_msi_irq(e, &irq);
> + kvm_set_msi_irq(kvm, e, &irq);
>
> return kvm_irq_delivery_to_apic(kvm, NULL, &irq, NULL);
> }
> @@ -153,7 +166,7 @@ int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
> if (unlikely(e->type != KVM_IRQ_ROUTING_MSI))
> return -EWOULDBLOCK;
>

Shouldn't we check the msi_route_invalid in kvm_arch_set_irq_inatomic?

> - kvm_set_msi_irq(e, &irq);
> + kvm_set_msi_irq(kvm, e, &irq);
>
> if (kvm_irq_delivery_to_apic_fast(kvm, NULL, &irq, &r, NULL))
> return r;
> @@ -286,6 +299,9 @@ int kvm_set_routing_entry(struct kvm *kvm,
> e->msi.address_lo = ue->u.msi.address_lo;
> e->msi.address_hi = ue->u.msi.address_hi;
> e->msi.data = ue->u.msi.data;
> +
> + if (kvm_msi_route_invalid(kvm, e))
> + goto out;
> break;
> case KVM_IRQ_ROUTING_HV_SINT:
> e->set = kvm_hv_set_sint;
> @@ -394,7 +410,7 @@ 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(vcpu->kvm, entry, &irq);
>
> 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 3c2a8c113054..b47a82bfc8c4 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1991,10 +1991,15 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
> if (apic_x2apic_mode(vcpu->arch.apic)) {
> u32 *id = (u32 *)(s->regs + APIC_ID);
>
> - if (set)
> - *id >>= 24;
> - else
> - *id <<= 24;
> + if (vcpu->kvm->arch.x2apic_api) {
> + if (*id != vcpu->vcpu_id)
> + return -EINVAL;
> + } else {
> + if (set)
> + *id >>= 24;
> + else
> + *id <<= 24;
> + }
> }
>
> return 0;
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 0a6a8845ea0c..ada9437d6e18 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(kvm, e, &irq);
> 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 b178c8c12717..5d4089dcb3eb 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 +3800,10 @@ split_irqchip_unlock:
> mutex_unlock(&kvm->lock);
> break;
> }
> + case KVM_CAP_X2APIC_API:
> + kvm->arch.x2apic_api = true;
> + r = 0;
> + break;
> default:
> r = -EINVAL;
> break;
> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
> index f28292d73ddb..8ade3eb6c640 100644
> --- a/include/trace/events/kvm.h
> +++ b/include/trace/events/kvm.h
> @@ -151,8 +151,9 @@ TRACE_EVENT(kvm_msi_set_irq,
> __entry->data = data;
> ),
>
> - TP_printk("dst %u vec %u (%s|%s|%s%s)",
> - (u8)(__entry->address >> 12), (u8)__entry->data,
> + TP_printk("dst %llx vec %u (%s|%s|%s%s)",
> + (u8)(__entry->address >> 12) | ((__entry->address >> 32) & 0xffffff00),
> + (u8)__entry->data,
> __print_symbolic((__entry->data >> 8 & 0x7), kvm_deliver_mode),
> (__entry->address & (1<<2)) ? "logical" : "physical",
> (__entry->data & (1<<15)) ? "level" : "edge",
> 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
>
>

--
best regards
yang