KVM: x86: Split the APIC from the rest of IRQCHIP.

First patch in a series which enables the relocation of the
PIC/IOAPIC to userspace.

Adds capability KVM_CAP_SPLIT_IRQCHIP;

KVM_CAP_SPLIT_IRQCHIP enables the construction of LAPICs without the
rest of the irqchip.

Compile tested for x86.

Signed-off-by: Steve Rutherford <srutherford@google.com>
Suggested-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 28c98c8f9d1c..f720774a4797 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2448,6 +2448,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
         case KVM_CAP_ENABLE_CAP_VM:
         case KVM_CAP_DISABLE_QUIRKS:
         case KVM_CAP_SET_BOOT_CPU_ID:
+        case KVM_CAP_SPLIT_IRQCHIP:
 #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
         case KVM_CAP_ASSIGN_DEV_IRQ:
         case KVM_CAP_PCI_2_3:
@@ -3555,6 +3556,24 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
                 kvm->arch.disabled_quirks = cap->args[0];
                 r = 0;
                 break;
+        case KVM_CAP_SPLIT_IRQCHIP: {
+                mutex_lock(&kvm->lock);
+                r = -EEXIST;
+                if (irqchip_in_kernel(kvm))
+                        goto split_irqchip_unlock;
+                if (atomic_read(&kvm->online_vcpus))
+                        goto split_irqchip_unlock;
+                r = kvm_setup_empty_irq_routing(kvm);
+                if (r)
+                        goto split_irqchip_unlock;
+                /* Pairs with irqchip_in_kernel. */
+                smp_wmb();
+                kvm->arch.irqchip_split = true;
+                r = 0;
+split_irqchip_unlock:
+                mutex_unlock(&kvm->lock);
+                break;
+        }
         default:
                 r = -EINVAL;
                 break;
@@ -3668,7 +3687,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 }
 
                 r = -ENXIO;
-                if (!irqchip_in_kernel(kvm))
+                if (!irqchip_in_kernel(kvm) || irqchip_split(kvm))
                         goto get_irqchip_out;
                 r = kvm_vm_ioctl_get_irqchip(kvm, chip);
                 if (r)
@@ -3692,7 +3711,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 }
 
                 r = -ENXIO;
-                if (!irqchip_in_kernel(kvm))
+                if (!irqchip_in_kernel(kvm) || irqchip_split(kvm))
                         goto set_irqchip_out;
                 r = kvm_vm_ioctl_set_irqchip(kvm, chip);
                 if (r)