kvm: add device control API

Currently, devices that are emulated inside KVM are configured in a
hardcoded manner based on an assumption that any given architecture
only has one way to do it.  If there's any need to access device state,
it is done through inflexible one-purpose-only IOCTLs (e.g.
KVM_GET/SET_LAPIC).  Defining new IOCTLs for every little thing is
cumbersome and depletes a limited numberspace.

This API provides a mechanism to instantiate a device of a certain
type, returning an ID that can be used to set/get attributes of the
device.  Attributes may include configuration parameters (e.g.
register base address), device state, operational commands, etc.  It
is similar to the ONE_REG API, except that it acts on devices rather
than vcpus.

Both device types and individual attributes can be tested without having
to create the device or get/set the attribute, without the need for
separately managing enumerated capabilities.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index dcef724f4ba6..6dab6b5b3e3b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1064,6 +1064,41 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
 
 extern bool kvm_rebooting;
 
+struct kvm_device_ops;
+
+struct kvm_device {
+	struct kvm_device_ops *ops;
+	struct kvm *kvm;
+	atomic_t users;
+	void *private;
+};
+
+/* create, destroy, and name are mandatory */
+struct kvm_device_ops {
+	const char *name;
+	int (*create)(struct kvm_device *dev, u32 type);
+
+	/*
+	 * Destroy is responsible for freeing dev.
+	 *
+	 * Destroy may be called before or after destructors are called
+	 * on emulated I/O regions, depending on whether a reference is
+	 * held by a vcpu or other kvm component that gets destroyed
+	 * after the emulated I/O.
+	 */
+	void (*destroy)(struct kvm_device *dev);
+
+	int (*set_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
+	int (*get_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
+	int (*has_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
+	long (*ioctl)(struct kvm_device *dev, unsigned int ioctl,
+		      unsigned long arg);
+};
+
+void kvm_device_get(struct kvm_device *dev);
+void kvm_device_put(struct kvm_device *dev);
+struct kvm_device *kvm_device_from_filp(struct file *filp);
+
 #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
 
 static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)