Re: [RFC PATCH 1/4] KVM: x86: Split the APIC from the rest of IRQCHIP.

[Steve Rutherford <srutherford@google.com>]

On Wed, May 13, 2015 at 09:57:00AM +0200, Paolo Bonzini wrote:
> 
> 
> On 13/05/2015 03:47, Steve Rutherford wrote:
> > First patch in a series which enables the relocation of the
> > PIC/IOAPIC/PIT to userspace.
> > 
> > Adds capability KVM_CAP_SPLIT_IRQCHIP and ioctl KVM_SPLIT_IRQCHIP.
> > 
> > KVM_SPLIT_IRQCHIP enables the construction of LAPICs without the rest
> > of the irqchip.
> 
> The ioctl name in the code is KVM_CREATE_SPLIT_IRQCHIP, but it doesn't
> seem to create a local APIC.
> 

 This enables the creation of LAPICs every time a VCPU is created, which I guess is different. I'll change the language to reflect that.

> > Compile tested for x86.
> 
> The capability is fine.  However, instead of introducing a new ioctl,
> you can use KVM_CAP_ENABLE_CAP_VM and enable the capability once
> (per-VM) using KVM_ENABLE_CAP.  The enabling code is basically the same
> you have in your code.
> 

ENABLE_CAP seems like a better way to go. I'll update this to use it instead of the IOCTL. 

Steve
> Paolo
> 
> > Signed-off-by: Steve Rutherford <srutherford@google.com>
> > Suggested-by: Andrew Honig <ahonig@google.com>
> > ---
> >  Documentation/virtual/kvm/api.txt | 15 ++++++++++++
> >  arch/powerpc/kvm/irq.h            |  5 ++++
> >  arch/s390/kvm/irq.h               |  4 ++++
> >  arch/x86/include/asm/kvm_host.h   |  2 ++
> >  arch/x86/kvm/assigned-dev.c       |  4 ++--
> >  arch/x86/kvm/irq.c                |  6 ++---
> >  arch/x86/kvm/irq.h                | 11 +++++++++
> >  arch/x86/kvm/irq_comm.c           |  7 ++++++
> >  arch/x86/kvm/lapic.c              | 13 +++++++----
> >  arch/x86/kvm/mmu.c                |  2 +-
> >  arch/x86/kvm/svm.c                |  4 ++--
> >  arch/x86/kvm/vmx.c                | 12 +++++-----
> >  arch/x86/kvm/x86.c                | 49 +++++++++++++++++++++++++++------------
> >  include/kvm/arm_vgic.h            |  1 +
> >  include/linux/kvm_host.h          |  1 +
> >  include/uapi/linux/kvm.h          |  3 +++
> >  virt/kvm/irqchip.c                |  2 +-
> >  17 files changed, 106 insertions(+), 35 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> > index 6955444..0744b4e 100644
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -2979,6 +2979,21 @@ len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0
> >  and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq),
> >  which is the maximum number of possibly pending cpu-local interrupts.
> >  
> > +4.96 KVM_SPLIT_IRQCHIP
> > +
> > +Capability: KVM_CAP_SPLIT_IRQCHIP
> > +Architectures: x86
> > +Type:  VM ioctl
> > +Parameters: None
> > +Returns: 0 on success, -1 on error
> > +
> > +Create a local apic for each processor in the kernel.  This differs from
> > +KVM_CREATE_IRQCHIP in that it only creates the local apic; it creates neither
> > +the ioapic nor the pic in the kernel. Also, enables in kernel routing of
> > +interrupt requests. Fails if VCPU has already been created, or if the irqchip is
> > +already in the kernel.
> > +
> > +
> >  5. The kvm_run structure
> >  ------------------------
> >  
> > diff --git a/arch/powerpc/kvm/irq.h b/arch/powerpc/kvm/irq.h
> > index 5a9a10b..5e6fa06 100644
> > --- a/arch/powerpc/kvm/irq.h
> > +++ b/arch/powerpc/kvm/irq.h
> > @@ -17,4 +17,9 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
> >  	return ret;
> >  }
> >  
> > +static inline int lapic_in_kernel(struct kvm *kvm)
> > +{
> > +	return irqchip_in_kernel(kvm);
> > +}
> > +
> >  #endif
> > diff --git a/arch/s390/kvm/irq.h b/arch/s390/kvm/irq.h
> > index d98e415..db876c3 100644
> > --- a/arch/s390/kvm/irq.h
> > +++ b/arch/s390/kvm/irq.h
> > @@ -19,4 +19,8 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
> >  	return 1;
> >  }
> >  
> > +static inline int lapic_in_kernel(struct kvm *kvm)
> > +{
> > +	return irqchip_in_kernel(kvm);
> > +}
> >  #endif
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index bbb8f4e..3ddc134 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -638,6 +638,8 @@ struct kvm_arch {
> >  	bool boot_vcpu_runs_old_kvmclock;
> >  
> >  	u64 disabled_quirks;
> > +
> > +	bool irqchip_split;
> >  };
> >  
> >  struct kvm_vm_stat {
> > diff --git a/arch/x86/kvm/assigned-dev.c b/arch/x86/kvm/assigned-dev.c
> > index d090ecf..1237e92 100644
> > --- a/arch/x86/kvm/assigned-dev.c
> > +++ b/arch/x86/kvm/assigned-dev.c
> > @@ -291,7 +291,7 @@ static int kvm_deassign_irq(struct kvm *kvm,
> >  {
> >  	unsigned long guest_irq_type, host_irq_type;
> >  
> > -	if (!irqchip_in_kernel(kvm))
> > +	if (!lapic_in_kernel(kvm))
> >  		return -EINVAL;
> >  	/* no irq assignment to deassign */
> >  	if (!assigned_dev->irq_requested_type)
> > @@ -568,7 +568,7 @@ static int kvm_vm_ioctl_assign_irq(struct kvm *kvm,
> >  	struct kvm_assigned_dev_kernel *match;
> >  	unsigned long host_irq_type, guest_irq_type;
> >  
> > -	if (!irqchip_in_kernel(kvm))
> > +	if (!lapic_in_kernel(kvm))
> >  		return r;
> >  
> >  	mutex_lock(&kvm->lock);
> > diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
> > index a1ec6a50..706e47a 100644
> > --- a/arch/x86/kvm/irq.c
> > +++ b/arch/x86/kvm/irq.c
> > @@ -57,7 +57,7 @@ static int kvm_cpu_has_extint(struct kvm_vcpu *v)
> >   */
> >  int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
> >  {
> > -	if (!irqchip_in_kernel(v->kvm))
> > +	if (!lapic_in_kernel(v->kvm))
> >  		return v->arch.interrupt.pending;
> >  
> >  	if (kvm_cpu_has_extint(v))
> > @@ -75,7 +75,7 @@ int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
> >   */
> >  int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
> >  {
> > -	if (!irqchip_in_kernel(v->kvm))
> > +	if (!lapic_in_kernel(v->kvm))
> >  		return v->arch.interrupt.pending;
> >  
> >  	if (kvm_cpu_has_extint(v))
> > @@ -103,7 +103,7 @@ int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
> >  {
> >  	int vector;
> >  
> > -	if (!irqchip_in_kernel(v->kvm))
> > +	if (!lapic_in_kernel(v->kvm))
> >  		return v->arch.interrupt.nr;
> >  
> >  	vector = kvm_cpu_get_extint(v);
> > diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
> > index ad68c73..e46abf3 100644
> > --- a/arch/x86/kvm/irq.h
> > +++ b/arch/x86/kvm/irq.h
> > @@ -92,6 +92,17 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
> >  	return ret;
> >  }
> >  
> > +static inline int irqchip_split(struct kvm *kvm)
> > +{
> > +	return kvm->arch.irqchip_split;
> > +}
> > +
> > +static inline int lapic_in_kernel(struct kvm *kvm)
> > +{
> > +	return irqchip_split(kvm) || irqchip_in_kernel(kvm);
> > +}
> > +
> > +
> >  void kvm_pic_reset(struct kvm_kpic_state *s);
> >  
> >  void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
> > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> > index 9efff9e..f43c59a 100644
> > --- a/arch/x86/kvm/irq_comm.c
> > +++ b/arch/x86/kvm/irq_comm.c
> > @@ -328,3 +328,10 @@ int kvm_setup_default_irq_routing(struct kvm *kvm)
> >  	return kvm_set_irq_routing(kvm, default_routing,
> >  				   ARRAY_SIZE(default_routing), 0);
> >  }
> > +
> > +static const struct kvm_irq_routing_entry empty_routing[] = {};
> > +
> > +int kvm_setup_empty_irq_routing(struct kvm *kvm)
> > +{
> > +	return kvm_set_irq_routing(kvm, empty_routing, 0, 0);
> > +}
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index dc5b57b..bc392a6 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -209,7 +209,8 @@ out:
> >  	if (old)
> >  		kfree_rcu(old, rcu);
> >  
> > -	kvm_vcpu_request_scan_ioapic(kvm);
> > +	if (!irqchip_split(kvm))
> > +		kvm_vcpu_request_scan_ioapic(kvm);
> >  }
> >  
> >  static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val)
> > @@ -1819,7 +1820,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
> >  		kvm_x86_ops->hwapic_isr_update(vcpu->kvm,
> >  				apic_find_highest_isr(apic));
> >  	kvm_make_request(KVM_REQ_EVENT, vcpu);
> > -	kvm_rtc_eoi_tracking_restore_one(vcpu);
> > +	if (!irqchip_split(vcpu->kvm))
> > +		kvm_rtc_eoi_tracking_restore_one(vcpu);
> >  }
> >  
> >  void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
> > @@ -1902,7 +1904,8 @@ static void apic_sync_pv_eoi_to_guest(struct kvm_vcpu *vcpu,
> >  	    /* Cache not set: could be safe but we don't bother. */
> >  	    apic->highest_isr_cache == -1 ||
> >  	    /* Need EOI to update ioapic. */
> > -	    kvm_ioapic_handles_vector(vcpu->kvm, apic->highest_isr_cache)) {
> > +	    kvm_ioapic_handles_vector(vcpu->kvm, apic->highest_isr_cache) ||
> > +	    irqchip_split(vcpu->kvm)) {
> >  		/*
> >  		 * PV EOI was disabled by apic_sync_pv_eoi_from_guest
> >  		 * so we need not do anything here.
> > @@ -1958,7 +1961,7 @@ int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> >  	struct kvm_lapic *apic = vcpu->arch.apic;
> >  	u32 reg = (msr - APIC_BASE_MSR) << 4;
> >  
> > -	if (!irqchip_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
> > +	if (!lapic_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
> >  		return 1;
> >  
> >  	if (reg == APIC_ICR2)
> > @@ -1975,7 +1978,7 @@ int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
> >  	struct kvm_lapic *apic = vcpu->arch.apic;
> >  	u32 reg = (msr - APIC_BASE_MSR) << 4, low, high = 0;
> >  
> > -	if (!irqchip_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
> > +	if (!lapic_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
> >  		return 1;
> >  
> >  	if (reg == APIC_DFR || reg == APIC_ICR2) {
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index b78e83f..e5bf6db 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -3465,7 +3465,7 @@ static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
> >  
> >  static bool can_do_async_pf(struct kvm_vcpu *vcpu)
> >  {
> > -	if (unlikely(!irqchip_in_kernel(vcpu->kvm) ||
> > +	if (unlikely(!lapic_in_kernel(vcpu->kvm) ||
> >  		     kvm_event_needs_reinjection(vcpu)))
> >  		return false;
> >  
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index 8954d7a..7ac9ec2 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -3054,7 +3054,7 @@ static int cr8_write_interception(struct vcpu_svm *svm)
> >  	u8 cr8_prev = kvm_get_cr8(&svm->vcpu);
> >  	/* instruction emulation calls kvm_set_cr8() */
> >  	r = cr_interception(svm);
> > -	if (irqchip_in_kernel(svm->vcpu.kvm))
> > +	if (lapic_in_kernel(svm->vcpu.kvm))
> >  		return r;
> >  	if (cr8_prev <= kvm_get_cr8(&svm->vcpu))
> >  		return r;
> > @@ -3295,7 +3295,7 @@ static int interrupt_window_interception(struct vcpu_svm *svm)
> >  	 * If the user space waits to inject interrupts, exit as soon as
> >  	 * possible
> >  	 */
> > -	if (!irqchip_in_kernel(svm->vcpu.kvm) &&
> > +	if (!lapic_in_kernel(svm->vcpu.kvm) &&
> >  	    kvm_run->request_interrupt_window &&
> >  	    !kvm_cpu_has_interrupt(&svm->vcpu)) {
> >  		kvm_run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index bcb61b0..a53747f 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -948,7 +948,7 @@ static inline bool cpu_has_vmx_tpr_shadow(void)
> >  
> >  static inline bool vm_need_tpr_shadow(struct kvm *kvm)
> >  {
> > -	return (cpu_has_vmx_tpr_shadow()) && (irqchip_in_kernel(kvm));
> > +	return (cpu_has_vmx_tpr_shadow()) && lapic_in_kernel(kvm);
> >  }
> >  
> >  static inline bool cpu_has_secondary_exec_ctrls(void)
> > @@ -1064,7 +1064,7 @@ static inline bool cpu_has_vmx_ple(void)
> >  
> >  static inline bool vm_need_virtualize_apic_accesses(struct kvm *kvm)
> >  {
> > -	return flexpriority_enabled && irqchip_in_kernel(kvm);
> > +	return flexpriority_enabled && lapic_in_kernel(kvm);
> >  }
> >  
> >  static inline bool cpu_has_vmx_vpid(void)
> > @@ -4341,7 +4341,7 @@ static void vmx_disable_intercept_msr_write_x2apic(u32 msr)
> >  
> >  static int vmx_vm_has_apicv(struct kvm *kvm)
> >  {
> > -	return enable_apicv && irqchip_in_kernel(kvm);
> > +	return enable_apicv && lapic_in_kernel(kvm);
> >  }
> >  
> >  static int vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
> > @@ -5317,7 +5317,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
> >  				u8 cr8 = (u8)val;
> >  				err = kvm_set_cr8(vcpu, cr8);
> >  				kvm_complete_insn_gp(vcpu, err);
> > -				if (irqchip_in_kernel(vcpu->kvm))
> > +				if (lapic_in_kernel(vcpu->kvm))
> >  					return 1;
> >  				if (cr8_prev <= cr8)
> >  					return 1;
> > @@ -5534,7 +5534,7 @@ static int handle_interrupt_window(struct kvm_vcpu *vcpu)
> >  	 * If the user space waits to inject interrupts, exit as soon as
> >  	 * possible
> >  	 */
> > -	if (!irqchip_in_kernel(vcpu->kvm) &&
> > +	if (!lapic_in_kernel(vcpu->kvm) &&
> >  	    vcpu->run->request_interrupt_window &&
> >  	    !kvm_cpu_has_interrupt(vcpu)) {
> >  		vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
> > @@ -9419,7 +9419,7 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
> >  	/* vmcs12's VM_ENTRY_LOAD_IA32_EFER and VM_ENTRY_IA32E_MODE are
> >  	 * emulated by vmx_set_efer(), below.
> >  	 */
> > -	vm_entry_controls_init(vmx, 
> > +	vm_entry_controls_init(vmx,
> >  		(vmcs12->vm_entry_controls & ~VM_ENTRY_LOAD_IA32_EFER &
> >  			~VM_ENTRY_IA32E_MODE) |
> >  		(vmcs_config.vmentry_ctrl & ~VM_ENTRY_IA32E_MODE));
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index cde5d61..7505b39 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -782,7 +782,7 @@ int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8)
> >  {
> >  	if (cr8 & CR8_RESERVED_BITS)
> >  		return 1;
> > -	if (irqchip_in_kernel(vcpu->kvm))
> > +	if (lapic_in_kernel(vcpu->kvm))
> >  		kvm_lapic_set_tpr(vcpu, cr8);
> >  	else
> >  		vcpu->arch.cr8 = cr8;
> > @@ -792,7 +792,7 @@ EXPORT_SYMBOL_GPL(kvm_set_cr8);
> >  
> >  unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu)
> >  {
> > -	if (irqchip_in_kernel(vcpu->kvm))
> > +	if (lapic_in_kernel(vcpu->kvm))
> >  		return kvm_lapic_get_cr8(vcpu);
> >  	else
> >  		return vcpu->arch.cr8;
> > @@ -2800,6 +2800,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >  	case KVM_CAP_TSC_DEADLINE_TIMER:
> >  	case KVM_CAP_ENABLE_CAP_VM:
> >  	case KVM_CAP_DISABLE_QUIRKS:
> > +	case KVM_CAP_SPLIT_IRQCHIP:
> >  #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
> >  	case KVM_CAP_ASSIGN_DEV_IRQ:
> >  	case KVM_CAP_PCI_2_3:
> > @@ -3002,7 +3003,7 @@ static int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
> >  {
> >  	if (irq->irq >= KVM_NR_INTERRUPTS)
> >  		return -EINVAL;
> > -	if (irqchip_in_kernel(vcpu->kvm))
> > +	if (lapic_in_kernel(vcpu->kvm))
> >  		return -ENXIO;
> >  
> >  	kvm_queue_interrupt(vcpu, irq->irq, false);
> > @@ -3480,7 +3481,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> >  		struct kvm_vapic_addr va;
> >  
> >  		r = -EINVAL;
> > -		if (!irqchip_in_kernel(vcpu->kvm))
> > +		if (!lapic_in_kernel(vcpu->kvm))
> >  			goto out;
> >  		r = -EFAULT;
> >  		if (copy_from_user(&va, argp, sizeof va))
> > @@ -3838,7 +3839,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> >  int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event,
> >  			bool line_status)
> >  {
> > -	if (!irqchip_in_kernel(kvm))
> > +	if (!lapic_in_kernel(kvm))
> >  		return -ENXIO;
> >  
> >  	irq_event->status = kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID,
> > @@ -4128,6 +4129,24 @@ long kvm_arch_vm_ioctl(struct file *filp,
> >  		r = kvm_vm_ioctl_enable_cap(kvm, &cap);
> >  		break;
> >  	}
> > +	case KVM_CREATE_SPLIT_IRQCHIP: {
> > +		mutex_lock(&kvm->lock);
> > +		r = -EEXIST;
> > +		if (lapic_in_kernel(kvm))
> > +			goto split_irqchip_unlock;
> > +		r = -EINVAL;
> > +		if (atomic_read(&kvm->online_vcpus))
> > +			goto split_irqchip_unlock;
> > +		r = kvm_setup_empty_irq_routing(kvm);
> > +		if (r)
> > +			goto split_irqchip_unlock;
> > +		kvm->arch.irqchip_split = true;
> > +		r = 0;
> > +split_irqchip_unlock:
> > +		mutex_unlock(&kvm->lock);
> > +		break;
> > +	}
> > +
> >  	default:
> >  		r = kvm_vm_ioctl_assigned_device(kvm, ioctl, arg);
> >  	}
> > @@ -5893,7 +5912,7 @@ void kvm_arch_exit(void)
> >  int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> >  {
> >  	++vcpu->stat.halt_exits;
> > -	if (irqchip_in_kernel(vcpu->kvm)) {
> > +	if (lapic_in_kernel(vcpu->kvm)) {
> >  		vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
> >  		return 1;
> >  	} else {
> > @@ -6060,7 +6079,7 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
> >   */
> >  static int dm_request_for_irq_injection(struct kvm_vcpu *vcpu)
> >  {
> > -	return (!irqchip_in_kernel(vcpu->kvm) && !kvm_cpu_has_interrupt(vcpu) &&
> > +	return (!lapic_in_kernel(vcpu->kvm) && !kvm_cpu_has_interrupt(vcpu) &&
> >  		vcpu->run->request_interrupt_window &&
> >  		kvm_arch_interrupt_allowed(vcpu));
> >  }
> > @@ -6072,7 +6091,7 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu)
> >  	kvm_run->if_flag = (kvm_get_rflags(vcpu) & X86_EFLAGS_IF) != 0;
> >  	kvm_run->cr8 = kvm_get_cr8(vcpu);
> >  	kvm_run->apic_base = kvm_get_apic_base(vcpu);
> > -	if (irqchip_in_kernel(vcpu->kvm))
> > +	if (lapic_in_kernel(vcpu->kvm))
> >  		kvm_run->ready_for_interrupt_injection = 1;
> >  	else
> >  		kvm_run->ready_for_interrupt_injection =
> > @@ -6219,7 +6238,7 @@ void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
> >  {
> >  	struct page *page = NULL;
> >  
> > -	if (!irqchip_in_kernel(vcpu->kvm))
> > +	if (!lapic_in_kernel(vcpu->kvm))
> >  		return;
> >  
> >  	if (!kvm_x86_ops->set_apic_access_page_addr)
> > @@ -6255,7 +6274,7 @@ void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm,
> >  static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> >  {
> >  	int r;
> > -	bool req_int_win = !irqchip_in_kernel(vcpu->kvm) &&
> > +	bool req_int_win = !lapic_in_kernel(vcpu->kvm) &&
> >  		vcpu->run->request_interrupt_window;
> >  	bool req_immediate_exit = false;
> >  
> > @@ -6644,7 +6663,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> >  	}
> >  
> >  	/* re-sync apic's tpr */
> > -	if (!irqchip_in_kernel(vcpu->kvm)) {
> > +	if (!lapic_in_kernel(vcpu->kvm)) {
> >  		if (kvm_set_cr8(vcpu, kvm_run->cr8) != 0) {
> >  			r = -EINVAL;
> >  			goto out;
> > @@ -7340,7 +7359,7 @@ void kvm_arch_check_processor_compat(void *rtn)
> >  
> >  bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
> >  {
> > -	return irqchip_in_kernel(vcpu->kvm) == (vcpu->arch.apic != NULL);
> > +	return lapic_in_kernel(vcpu->kvm) == (vcpu->arch.apic != NULL);
> >  }
> >  
> >  struct static_key kvm_no_apic_vcpu __read_mostly;
> > @@ -7356,7 +7375,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
> >  
> >  	vcpu->arch.pv.pv_unhalted = false;
> >  	vcpu->arch.emulate_ctxt.ops = &emulate_ops;
> > -	if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_reset_bsp(vcpu))
> > +	if (!lapic_in_kernel(kvm) || kvm_vcpu_is_reset_bsp(vcpu))
> >  		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> >  	else
> >  		vcpu->arch.mp_state = KVM_MP_STATE_UNINITIALIZED;
> > @@ -7374,7 +7393,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
> >  	if (r < 0)
> >  		goto fail_free_pio_data;
> >  
> > -	if (irqchip_in_kernel(kvm)) {
> > +	if (lapic_in_kernel(kvm)) {
> >  		r = kvm_create_lapic(vcpu);
> >  		if (r < 0)
> >  			goto fail_mmu_destroy;
> > @@ -7437,7 +7456,7 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
> >  	kvm_mmu_destroy(vcpu);
> >  	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> >  	free_page((unsigned long)vcpu->arch.pio_data);
> > -	if (!irqchip_in_kernel(vcpu->kvm))
> > +	if (!lapic_in_kernel(vcpu->kvm))
> >  		static_key_slow_dec(&kvm_no_apic_vcpu);
> >  }
> >  
> > diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> > index 133ea00..ffe1f4e 100644
> > --- a/include/kvm/arm_vgic.h
> > +++ b/include/kvm/arm_vgic.h
> > @@ -329,6 +329,7 @@ int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
> >  int kvm_vgic_vcpu_active_irq(struct kvm_vcpu *vcpu);
> >  
> >  #define irqchip_in_kernel(k)	(!!((k)->arch.vgic.in_kernel))
> > +#define lapic_in_kernel(k)      (irqchip_in_kernel(k))
> >  #define vgic_initialized(k)	(!!((k)->arch.vgic.nr_cpus))
> >  #define vgic_ready(k)		((k)->arch.vgic.ready)
> >  
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 87fd74a..277b7a1 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -934,6 +934,7 @@ static inline int mmu_notifier_retry(struct kvm *kvm, unsigned long mmu_seq)
> >  #endif
> >  
> >  int kvm_setup_default_irq_routing(struct kvm *kvm);
> > +int kvm_setup_empty_irq_routing(struct kvm *kvm);
> >  int kvm_set_irq_routing(struct kvm *kvm,
> >  			const struct kvm_irq_routing_entry *entries,
> >  			unsigned nr,
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 75bd9f7..7d06dc4 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -815,6 +815,7 @@ struct kvm_ppc_smmu_info {
> >  #define KVM_CAP_S390_IRQ_STATE 114
> >  #define KVM_CAP_PPC_HWRNG 115
> >  #define KVM_CAP_DISABLE_QUIRKS 116
> > +#define KVM_CAP_SPLIT_IRQCHIP 117
> >  
> >  #ifdef KVM_CAP_IRQ_ROUTING
> >  
> > @@ -1200,6 +1201,8 @@ struct kvm_s390_ucas_mapping {
> >  /* Available with KVM_CAP_S390_IRQ_STATE */
> >  #define KVM_S390_SET_IRQ_STATE	  _IOW(KVMIO, 0xb5, struct kvm_s390_irq_state)
> >  #define KVM_S390_GET_IRQ_STATE	  _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
> > +/* Available with KVM_CAP_SPLIT_IRQCHIP */
> > +#define KVM_CREATE_SPLIT_IRQCHIP  _IO(KVMIO, 0xb7)
> >  
> >  #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
> >  #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
> > diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
> > index 1d56a90..8aaceed 100644
> > --- a/virt/kvm/irqchip.c
> > +++ b/virt/kvm/irqchip.c
> > @@ -73,7 +73,7 @@ int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
> >  {
> >  	struct kvm_kernel_irq_routing_entry route;
> >  
> > -	if (!irqchip_in_kernel(kvm) || msi->flags != 0)
> > +	if (!lapic_in_kernel(kvm) || msi->flags != 0)
> >  		return -EINVAL;
> >  
> >  	route.msi.address_lo = msi->address_lo;
> >