Re: [PATCH v2 24/30] vfio-pci/zdev: wire up group notifier

[Pierre Morel <pmorel@linux.ibm.com>]

On 1/14/22 21:31, Matthew Rosato 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@linux.ibm.com>
> ---
>   arch/s390/include/asm/kvm_pci.h  |  2 ++
>   drivers/vfio/pci/vfio_pci_core.c |  2 ++
>   drivers/vfio/pci/vfio_pci_zdev.c | 46 ++++++++++++++++++++++++++++++++
>   include/linux/vfio_pci_core.h    | 10 +++++++
>   4 files changed, 60 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index fa90729a35cf..97a90b37c87d 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;
>   };
>   
>   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..5c2bddc57b39 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 +137,48 @@ 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;
> +		kvm_s390_pci_attach_kvm(kzdev->zdev, data);

Why not just set kzdev->kvm = data ?

alternatively, define kvm_s390_pci_attach_kvm() as an inline instead of 
a global function.

otherwise LGTM

> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +void 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);
> +
> +	if (!zdev)
> +		return;
> +
> +	if (kvm_s390_pci_dev_open(zdev))
> +		return;
> +
> +	zdev->kzdev->nb.notifier_call = vfio_pci_zdev_group_notifier;
> +
> +	if (vfio_register_notifier(vdev->vdev.dev, VFIO_GROUP_NOTIFY,
> +				   &events, &zdev->kzdev->nb))
> +		kvm_s390_pci_dev_release(zdev);
> +}
> +
> +void vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +
> +	if (!zdev || !zdev->kzdev)
> +		return;
> +
> +	vfio_unregister_notifier(vdev->vdev.dev, VFIO_GROUP_NOTIFY,
> +				 &zdev->kzdev->nb);
> +
> +	kvm_s390_pci_dev_release(zdev);
> +}
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index 5e2bca3b89db..05287f8ac855 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -198,12 +198,22 @@ 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);
> +void vfio_pci_zdev_open(struct vfio_pci_core_device *vdev);
> +void 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 void vfio_pci_zdev_open(struct vfio_pci_core_device *vdev)
> +{
> +}
> +
> +static inline void vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> +{
> +}
>   #endif
>   
>   /* Will be exported for vfio pci drivers usage */
> 

-- 
Pierre Morel
IBM Lab Boeblingen