KVM: arm/arm64: vgic: add init entry to VGIC KVM device

Since the advent of VGIC dynamic initialization, this latter is
initialized quite late on the first vcpu run or "on-demand", when
injecting an IRQ or when the guest sets its registers.

This initialization could be initiated explicitly much earlier
by the users-space, as soon as it has provided the requested
dimensioning parameters.

This patch adds a new entry to the VGIC KVM device that allows
the user to manually request the VGIC init:
- a new KVM_DEV_ARM_VGIC_GRP_CTRL group is introduced.
- Its first attribute is KVM_DEV_ARM_VGIC_CTRL_INIT

The rationale behind introducing a group is to be able to add other
controls later on, if needed.

Signed-off-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Documentation/virtual/kvm/devices/arm-vgic.txt

@@ -81,3 +81,14 @@ Groups:
     -EINVAL: Value set is out of the expected range
     -EBUSY: Value has already be set, or GIC has already been initialized
             with default values.
+
+  KVM_DEV_ARM_VGIC_GRP_CTRL
+  Attributes:
+    KVM_DEV_ARM_VGIC_CTRL_INIT
+      request the initialization of the VGIC, no additional parameter in
+      kvm_device_attr.addr.
+  Errors:
+    -ENXIO: VGIC not properly configured as required prior to calling
+     this attribute
+    -ENODEV: no online VCPU
+    -ENOMEM: memory shortage when allocating vgic internal data

arch/arm/include/uapi/asm/kvm.h

@@ -175,6 +175,8 @@ struct kvm_arch_memory_slot {
 #define   KVM_DEV_ARM_VGIC_OFFSET_SHIFT	0
 #define   KVM_DEV_ARM_VGIC_OFFSET_MASK	(0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
 #define KVM_DEV_ARM_VGIC_GRP_NR_IRQS	3
+#define KVM_DEV_ARM_VGIC_GRP_CTRL       4
+#define   KVM_DEV_ARM_VGIC_CTRL_INIT    0
 
 /* KVM_IRQ_LINE irq field index values */
 #define KVM_ARM_IRQ_TYPE_SHIFT		24

arch/arm64/include/uapi/asm/kvm.h

@@ -161,6 +161,8 @@ struct kvm_arch_memory_slot {
 #define   KVM_DEV_ARM_VGIC_OFFSET_SHIFT	0
 #define   KVM_DEV_ARM_VGIC_OFFSET_MASK	(0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
 #define KVM_DEV_ARM_VGIC_GRP_NR_IRQS	3
+#define KVM_DEV_ARM_VGIC_GRP_CTRL	4
+#define   KVM_DEV_ARM_VGIC_CTRL_INIT	0
 
 /* KVM_IRQ_LINE irq field index values */
 #define KVM_ARM_IRQ_TYPE_SHIFT		24

virt/kvm/arm/vgic.c

@@ -2302,7 +2302,14 @@ static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 
 		return ret;
 	}
-
+	case KVM_DEV_ARM_VGIC_GRP_CTRL: {
+		switch (attr->attr) {
+		case KVM_DEV_ARM_VGIC_CTRL_INIT:
+			r = vgic_init(dev->kvm);
+			return r;
+		}
+		break;
+	}
 	}
 
 	return -ENXIO;
@@ -2381,6 +2388,11 @@ static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 		return vgic_has_attr_regs(vgic_cpu_ranges, offset);
 	case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
 		return 0;
+	case KVM_DEV_ARM_VGIC_GRP_CTRL:
+		switch (attr->attr) {
+		case KVM_DEV_ARM_VGIC_CTRL_INIT:
+			return 0;
+		}
 	}
 	return -ENXIO;
 }