KVM: ARM: Introduce KVM_ARM_SET_DEVICE_ADDR ioctl

On ARM some bits are specific to the model being emulated for the guest and
user space needs a way to tell the kernel about those bits.  An example is mmio
device base addresses, where KVM must know the base address for a given device
to properly emulate mmio accesses within a certain address range or directly
map a device with virtualiation extensions into the guest address space.

We make this API ARM-specific as we haven't yet reached a consensus for a
generic API for all KVM architectures that will allow us to do something like
this.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/virtual/kvm/api.txt

@@ -2210,6 +2210,43 @@ This ioctl returns the guest registers that are supported for the
 KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
 
 
+4.80 KVM_ARM_SET_DEVICE_ADDR
+
+Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
+Architectures: arm
+Type: vm ioctl
+Parameters: struct kvm_arm_device_address (in)
+Returns: 0 on success, -1 on error
+Errors:
+  ENODEV: The device id is unknown
+  ENXIO:  Device not supported on current system
+  EEXIST: Address already set
+  E2BIG:  Address outside guest physical address space
+
+struct kvm_arm_device_addr {
+	__u64 id;
+	__u64 addr;
+};
+
+Specify a device address in the guest's physical address space where guests
+can access emulated or directly exposed devices, which the host kernel needs
+to know about. The id field is an architecture specific identifier for a
+specific device.
+
+ARM divides the id field into two parts, a device id and an address type id
+specific to the individual device.
+
+  bits:  | 63        ...       32 | 31    ...    16 | 15    ...    0 |
+  field: |        0x00000000      |     device id   |  addr type id  |
+
+ARM currently only require this when using the in-kernel GIC support for the
+hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2 as the device id.  When
+setting the base address for the guest's mapping of the VGIC virtual CPU
+and distributor interface, the ioctl must be called after calling
+KVM_CREATE_IRQCHIP, but before calling KVM_RUN on any of the VCPUs.  Calling
+this ioctl twice for any of the base addresses will return -EEXIST.
+
+
 5. The kvm_run structure
 ------------------------
 

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

@@ -65,6 +65,19 @@ struct kvm_regs {
 #define KVM_ARM_TARGET_CORTEX_A15	0
 #define KVM_ARM_NUM_TARGETS		1
 
+/* KVM_ARM_SET_DEVICE_ADDR ioctl id encoding */
+#define KVM_ARM_DEVICE_TYPE_SHIFT	0
+#define KVM_ARM_DEVICE_TYPE_MASK	(0xffff << KVM_ARM_DEVICE_TYPE_SHIFT)
+#define KVM_ARM_DEVICE_ID_SHIFT		16
+#define KVM_ARM_DEVICE_ID_MASK		(0xffff << KVM_ARM_DEVICE_ID_SHIFT)
+
+/* Supported device IDs */
+#define KVM_ARM_DEVICE_VGIC_V2		0
+
+/* Supported VGIC address types  */
+#define KVM_VGIC_V2_ADDR_TYPE_DIST	0
+#define KVM_VGIC_V2_ADDR_TYPE_CPU	1
+
 #define KVM_ARM_VCPU_POWER_OFF		0 /* CPU is started in OFF state */
 
 struct kvm_vcpu_init {

arch/arm/kvm/arm.c

@@ -167,6 +167,8 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_COALESCED_MMIO:
 		r = KVM_COALESCED_MMIO_PAGE_OFFSET;
 		break;
+	case KVM_CAP_ARM_SET_DEVICE_ADDR:
+		r = 1;
 	case KVM_CAP_NR_VCPUS:
 		r = num_online_cpus();
 		break;
@@ -827,10 +829,29 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
 	return -EINVAL;
 }
 
+static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
+					struct kvm_arm_device_addr *dev_addr)
+{
+	return -ENODEV;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
+	struct kvm *kvm = filp->private_data;
+	void __user *argp = (void __user *)arg;
+
+	switch (ioctl) {
+	case KVM_ARM_SET_DEVICE_ADDR: {
+		struct kvm_arm_device_addr dev_addr;
+
+		if (copy_from_user(&dev_addr, argp, sizeof(dev_addr)))
+			return -EFAULT;
+		return kvm_vm_ioctl_set_device_addr(kvm, &dev_addr);
+	}
+	default:
 		return -EINVAL;
+	}
 }
 
 static void cpu_init_hyp_mode(void *vector)

include/uapi/linux/kvm.h

@@ -637,6 +637,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_BOOKE_WATCHDOG 83
 #define KVM_CAP_PPC_HTAB_FD 84
 #define KVM_CAP_ARM_PSCI 87
+#define KVM_CAP_ARM_SET_DEVICE_ADDR 88
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -784,6 +785,11 @@ struct kvm_msi {
 	__u8  pad[16];
 };
 
+struct kvm_arm_device_addr {
+	__u64 id;
+	__u64 addr;
+};
+
 /*
  * ioctls for VM fds
  */
@@ -869,6 +875,8 @@ struct kvm_s390_ucas_mapping {
 #define KVM_ALLOCATE_RMA	  _IOR(KVMIO,  0xa9, struct kvm_allocate_rma)
 /* Available with KVM_CAP_PPC_HTAB_FD */
 #define KVM_PPC_GET_HTAB_FD	  _IOW(KVMIO,  0xaa, struct kvm_get_htab_fd)
+/* Available with KVM_CAP_ARM_SET_DEVICE_ADDR */
+#define KVM_ARM_SET_DEVICE_ADDR	  _IOW(KVMIO,  0xab, struct kvm_arm_device_addr)
 
 /*
  * ioctls for vcpu fds