arm/arm64: KVM: vgic: make number of irqs a configurable attribute

In order to make the number of interrupts configurable, use the new
fancy device management API to add KVM_DEV_ARM_VGIC_GRP_NR_IRQS as
a VGIC configurable attribute.

Userspace can now specify the exact size of the GIC (by increments
of 32 interrupts).

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index ac2b44d58e60..b6fab0f25f3b 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -2253,6 +2253,36 @@ static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 
                 return vgic_attr_regs_access(dev, attr, &reg, true);
         }
+        case KVM_DEV_ARM_VGIC_GRP_NR_IRQS: {
+                u32 __user *uaddr = (u32 __user *)(long)attr->addr;
+                u32 val;
+                int ret = 0;
+
+                if (get_user(val, uaddr))
+                        return -EFAULT;
+
+                /*
+                 * We require:
+                 * - at least 32 SPIs on top of the 16 SGIs and 16 PPIs
+                 * - at most 1024 interrupts
+                 * - a multiple of 32 interrupts
+                 */
+                if (val < (VGIC_NR_PRIVATE_IRQS + 32) ||
+                    val > VGIC_MAX_IRQS ||
+                    (val & 31))
+                        return -EINVAL;
+
+                mutex_lock(&dev->kvm->lock);
+
+                if (vgic_initialized(dev->kvm) || dev->kvm->arch.vgic.nr_irqs)
+                        ret = -EBUSY;
+                else
+                        dev->kvm->arch.vgic.nr_irqs = val;
+
+                mutex_unlock(&dev->kvm->lock);
+
+                return ret;
+        }
 
         }
 
@@ -2289,6 +2319,11 @@ static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
                 r = put_user(reg, uaddr);
                 break;
         }
+        case KVM_DEV_ARM_VGIC_GRP_NR_IRQS: {
+                u32 __user *uaddr = (u32 __user *)(long)attr->addr;
+                r = put_user(dev->kvm->arch.vgic.nr_irqs, uaddr);
+                break;
+        }
 
         }
 
@@ -2325,6 +2360,8 @@ static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
         case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
                 offset = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
                 return vgic_has_attr_regs(vgic_cpu_ranges, offset);
+        case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
+                return 0;
         }
         return -ENXIO;
 }