[v3 4/5] vfio: implement APIs to set/put kvm to/from vfio group

[Jike Song <jike.song@intel.com>]

A vfio_group may be or may not be attached to a KVM instance,
if it is, the user of vfio_group might also want to know which
KVM instance it is attached to, to utilize features provided
by KVM. In VFIO there are already external APIs for KVM to
get/put the vfio_group, by extending that, KVM can set or clear
itself to/from the vfio_group, for external users to use.

Signed-off-by: Jike Song <jike.song@intel.com>
---
 drivers/vfio/vfio.c  | 30 ++++++++++++++++++++++++++++++
 include/linux/vfio.h |  4 ++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index e3e58e3..41611cc 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -34,6 +34,7 @@
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
 #include <linux/wait.h>
+#include <linux/kvm_host.h>
 
 #define DRIVER_VERSION	"0.3"
 #define DRIVER_AUTHOR	"Alex Williamson <alex.williamson@redhat.com>"
@@ -86,6 +87,10 @@ struct vfio_group {
 	struct mutex			unbound_lock;
 	atomic_t			opened;
 	bool				noiommu;
+	struct {
+		struct kvm *kvm;
+		struct mutex lock;
+	} udata;
 };
 
 struct vfio_device {
@@ -333,6 +338,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
 	mutex_init(&group->device_lock);
 	INIT_LIST_HEAD(&group->unbound_list);
 	mutex_init(&group->unbound_lock);
+	mutex_init(&group->udata.lock);
 	atomic_set(&group->container_users, 0);
 	atomic_set(&group->opened, 0);
 	group->iommu_group = iommu_group;
@@ -1739,6 +1745,30 @@ long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
 }
 EXPORT_SYMBOL_GPL(vfio_external_check_extension);
 
+void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
+{
+	mutex_lock(&group->udata.lock);
+	group->udata.kvm = kvm;
+	mutex_unlock(&group->udata.lock);
+}
+EXPORT_SYMBOL_GPL(vfio_group_set_kvm);
+
+struct kvm *vfio_group_get_kvm(struct vfio_group *group)
+{
+	struct kvm *kvm = NULL;
+
+	mutex_lock(&group->udata.lock);
+
+	kvm = group->udata.kvm;
+	if (kvm)
+		kvm_get_kvm(kvm);
+
+	mutex_unlock(&group->udata.lock);
+
+	return kvm;
+}
+EXPORT_SYMBOL_GPL(vfio_group_get_kvm);
+
 /**
  * Sub-module support
  */
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index ad9b857..3abd690 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -95,6 +95,10 @@ extern long vfio_external_check_extension(struct vfio_group *group,
 extern struct vfio_group *vfio_group_get_from_dev(struct device *dev);
 extern void vfio_group_put(struct vfio_group *group);
 
+struct kvm;
+extern void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
+extern struct kvm *vfio_group_get_kvm(struct vfio_group *group);
+
 /*
  * Sub-module helpers
  */
-- 
1.9.1