Re: [PATCH 26/32] vfio-pci/zdev: wire up group notifier

[Alex Williamson]

On Tue,  7 Dec 2021 15:57:37 -0500
Matthew Rosato <mjrosato@xxxxxxxxxxxxx> wrote:

> KVM zPCI passthrough device logic will need a reference to the associated
> kvm guest that has access to the device.  Let's register a group notifier
> for VFIO_GROUP_NOTIFY_SET_KVM to catch this information in order to create
> an association between a kvm guest and the host zdev.
> 
> Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> ---
>  arch/s390/include/asm/kvm_pci.h  |  2 ++
>  drivers/vfio/pci/vfio_pci_core.c |  2 ++
>  drivers/vfio/pci/vfio_pci_zdev.c | 54 ++++++++++++++++++++++++++++++++
>  include/linux/vfio_pci_core.h    | 12 +++++++
>  4 files changed, 70 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index 97e3a369135d..6526908ac834 100644
> --- a/arch/s390/include/asm/kvm_pci.h
> +++ b/arch/s390/include/asm/kvm_pci.h
> @@ -17,6 +17,7 @@
>  #include <linux/kvm.h>
>  #include <linux/pci.h>
>  #include <linux/mutex.h>
> +#include <linux/notifier.h>
>  #include <asm/pci_insn.h>
>  #include <asm/pci_dma.h>
>  
> @@ -33,6 +34,7 @@ struct kvm_zdev {
>  	u64 rpcit_count;
>  	struct kvm_zdev_ioat ioat;
>  	struct zpci_fib fib;
> +	struct notifier_block nb;
>  };
>  
>  extern int kvm_s390_pci_dev_open(struct zpci_dev *zdev);
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index f948e6cd2993..fc57d4d0abbe 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -452,6 +452,7 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev)
>  
>  	vfio_pci_vf_token_user_add(vdev, -1);
>  	vfio_spapr_pci_eeh_release(vdev->pdev);
> +	vfio_pci_zdev_release(vdev);
>  	vfio_pci_core_disable(vdev);
>  
>  	mutex_lock(&vdev->igate);
> @@ -470,6 +471,7 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_close_device);
>  void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev)
>  {
>  	vfio_pci_probe_mmaps(vdev);
> +	vfio_pci_zdev_open(vdev);
>  	vfio_spapr_pci_eeh_open(vdev->pdev);
>  	vfio_pci_vf_token_user_add(vdev, 1);
>  }
> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
> index ea4c0d2b0663..cfd7f44b06c1 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -13,6 +13,7 @@
>  #include <linux/vfio_zdev.h>
>  #include <asm/pci_clp.h>
>  #include <asm/pci_io.h>
> +#include <asm/kvm_pci.h>
>  
>  #include <linux/vfio_pci_core.h>
>  
> @@ -136,3 +137,56 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
>  
>  	return ret;
>  }
> +
> +static int vfio_pci_zdev_group_notifier(struct notifier_block *nb,
> +					unsigned long action, void *data)
> +{
> +	struct kvm_zdev *kzdev = container_of(nb, struct kvm_zdev, nb);
> +
> +	if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
> +		if (!data || !kzdev->zdev)
> +			return NOTIFY_DONE;
> +		if (kvm_s390_pci_attach_kvm(kzdev->zdev, data))
> +			return NOTIFY_DONE;
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +int vfio_pci_zdev_open(struct vfio_pci_core_device *vdev)
> +{
> +	unsigned long events = VFIO_GROUP_NOTIFY_SET_KVM;
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +	int ret;
> +
> +	if (!zdev)
> +		return -ENODEV;
> +
> +	ret = kvm_s390_pci_dev_open(zdev);
> +	if (ret)
> +		return -ENODEV;
> +
> +	zdev->kzdev->nb.notifier_call = vfio_pci_zdev_group_notifier;
> +
> +	ret = vfio_register_notifier(vdev->vdev.dev, VFIO_GROUP_NOTIFY,
> +				     &events, &zdev->kzdev->nb);
> +	if (ret)
> +		kvm_s390_pci_dev_release(zdev);
> +
> +	return ret;

None of these error return paths are realized by the call site.  Thanks,

Alex

> +}
> +
> +int vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +
> +	if (!zdev || !zdev->kzdev)
> +		return -ENODEV;
> +
> +	vfio_unregister_notifier(vdev->vdev.dev, VFIO_GROUP_NOTIFY,
> +				 &zdev->kzdev->nb);
> +
> +	kvm_s390_pci_dev_release(zdev);
> +
> +	return 0;
> +}
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index 5e2bca3b89db..14079da409f1 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -198,12 +198,24 @@ static inline int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
>  #ifdef CONFIG_VFIO_PCI_ZDEV
>  extern int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
>  				       struct vfio_info_cap *caps);
> +int vfio_pci_zdev_open(struct vfio_pci_core_device *vdev);
> +int vfio_pci_zdev_release(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(struct vfio_pci_core_device *vdev)
> +{
> +	return -ENODEV;
> +}
> +
> +static inline int vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> +{
> +	return -ENODEV;
> +}
>  #endif
>  
>  /* Will be exported for vfio pci drivers usage */