virtio: Save negotiated features

We're going to need the features bits negotiated between host and guest in
the core code. Save them in the virtio_device structure.
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

include/kvm/virtio.h

@@ -141,6 +141,7 @@ struct virtio_device {
 	void			*virtio;
 	struct virtio_ops	*ops;
 	u16			endian;
+	u32			features;
 };
 
 struct virtio_ops {
@@ -180,4 +181,7 @@ static inline void virtio_init_device_vq(struct virtio_device *vdev,
 	vq->endian = vdev->endian;
 }
 
+void virtio_set_guest_features(struct kvm *kvm, struct virtio_device *vdev,
+			       void *dev, u32 features);
+
 #endif /* KVM__VIRTIO_H */

virtio/core.c

@@ -198,6 +198,15 @@ bool virtio_queue__should_signal(struct virt_queue *vq)
 	return false;
 }
 
+void virtio_set_guest_features(struct kvm *kvm, struct virtio_device *vdev,
+			       void *dev, u32 features)
+{
+	/* TODO: fail negotiation if features & ~host_features */
+
+	vdev->features = features;
+	vdev->ops->set_guest_features(kvm, dev, features);
+}
+
 int virtio_init(struct kvm *kvm, void *dev, struct virtio_device *vdev,
 		struct virtio_ops *ops, enum virtio_trans trans,
 		int device_id, int subsys_id, int class)

virtio/mmio.c

@@ -168,8 +168,8 @@ static void virtio_mmio_config_out(struct kvm_cpu *vcpu,
 	case VIRTIO_MMIO_GUEST_FEATURES:
 		if (vmmio->hdr.guest_features_sel == 0) {
 			val = ioport__read32(data);
-			vdev->ops->set_guest_features(vmmio->kvm,
-						      vmmio->dev, val);
+			virtio_set_guest_features(vmmio->kvm, vdev,
+						  vmmio->dev, val);
 		}
 		break;
 	case VIRTIO_MMIO_GUEST_PAGE_SIZE:

virtio/pci.c

@@ -267,7 +267,7 @@ static bool virtio_pci__io_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16
 	switch (offset) {
 	case VIRTIO_PCI_GUEST_FEATURES:
 		val = ioport__read32(data);
-		vdev->ops->set_guest_features(kvm, vpci->dev, val);
+		virtio_set_guest_features(kvm, vdev, vpci->dev, val);
 		break;
 	case VIRTIO_PCI_QUEUE_PFN:
 		val = ioport__read32(data);