vfio-pci/zdev: add open/close device hooks

During vfio-pci open_device, pass the KVM associated with the vfio group
(if one exists).  This is needed in order to pass a special indicator
(GISA) to firmware to allow zPCI interpretation facilities to be used
for only the specific KVM associated with the vfio-pci device.  During
vfio-pci close_device, unregister the notifier.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Link: https://lore.kernel.org/r/20220606203325.110625-18-mjrosato@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

drivers/vfio/pci/vfio_pci_core.c

@@ -316,10 +316,14 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev)
 		pci_write_config_word(pdev, PCI_COMMAND, cmd);
 	}
 
-	ret = vfio_config_init(vdev);
+	ret = vfio_pci_zdev_open_device(vdev);
 	if (ret)
 		goto out_free_state;
 
+	ret = vfio_config_init(vdev);
+	if (ret)
+		goto out_free_zdev;
+
 	msix_pos = pdev->msix_cap;
 	if (msix_pos) {
 		u16 flags;
@@ -340,6 +344,8 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev)
 
 	return 0;
 
+out_free_zdev:
+	vfio_pci_zdev_close_device(vdev);
 out_free_state:
 	kfree(vdev->pci_saved_state);
 	vdev->pci_saved_state = NULL;
@@ -418,6 +424,8 @@ void vfio_pci_core_disable(struct vfio_pci_core_device *vdev)
 
 	vdev->needs_reset = true;
 
+	vfio_pci_zdev_close_device(vdev);
+
 	/*
 	 * If we have saved state, restore it.  If we can reset the device,
 	 * even better.  Resetting with current state seems better than

drivers/vfio/pci/vfio_pci_zdev.c

@@ -11,6 +11,7 @@
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
 #include <linux/vfio_zdev.h>
+#include <linux/kvm_host.h>
 #include <asm/pci_clp.h>
 #include <asm/pci_io.h>
 
@@ -136,3 +137,26 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 
 	return ret;
 }
+
+int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+
+	if (!zdev)
+		return -ENODEV;
+
+	if (!vdev->vdev.kvm)
+		return 0;
+
+	return kvm_s390_pci_register_kvm(zdev, vdev->vdev.kvm);
+}
+
+void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+
+	if (!zdev || !vdev->vdev.kvm)
+		return;
+
+	kvm_s390_pci_unregister_kvm(zdev);
+}

include/linux/vfio_pci_core.h

@@ -209,12 +209,22 @@ static inline int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
 #ifdef CONFIG_VFIO_PCI_ZDEV_KVM
 extern int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 				       struct vfio_info_cap *caps);
+int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev);
+void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev);
 #else
 static inline int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 					      struct vfio_info_cap *caps)
 {
 	return -ENODEV;
 }
+
+static inline int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
+{
+	return 0;
+}
+
+static inline void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
+{}
 #endif
 
 /* Will be exported for vfio pci drivers usage */