linux-kernel - Re: [PATCH v1 5/6] vfio-pci/zdev: Perform platform specific function reset for zPCI

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Message-ID: <20250813143034.36f8c3a4.alex.williamson@redhat.com>
Date: Wed, 13 Aug 2025 14:30:34 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Farhan Ali <alifm@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, schnelle@...ux.ibm.com,
 mjrosato@...ux.ibm.com
Subject: Re: [PATCH v1 5/6] vfio-pci/zdev: Perform platform specific
 function reset for zPCI

On Wed, 13 Aug 2025 10:08:19 -0700
Farhan Ali <alifm@...ux.ibm.com> wrote:

> For zPCI devices we should drive a platform specific function reset
> as part of VFIO_DEVICE_RESET. This reset is needed recover a zPCI device
> in error state.
> 
> Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
> ---
>  arch/s390/pci/pci.c              |  1 +
>  drivers/vfio/pci/vfio_pci_core.c |  4 ++++
>  drivers/vfio/pci/vfio_pci_priv.h |  5 ++++
>  drivers/vfio/pci/vfio_pci_zdev.c | 39 ++++++++++++++++++++++++++++++++
>  4 files changed, 49 insertions(+)
> 
> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> index f795e05b5001..860a64993b58 100644
> --- a/arch/s390/pci/pci.c
> +++ b/arch/s390/pci/pci.c
> @@ -788,6 +788,7 @@ int zpci_hot_reset_device(struct zpci_dev *zdev)
>  
>  	return rc;
>  }
> +EXPORT_SYMBOL_GPL(zpci_hot_reset_device);
>  
>  /**
>   * zpci_create_device() - Create a new zpci_dev and add it to the zbus
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 7dcf5439dedc..7220a22135a9 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1227,6 +1227,10 @@ static int vfio_pci_ioctl_reset(struct vfio_pci_core_device *vdev,
>  	 */
>  	vfio_pci_set_power_state(vdev, PCI_D0);
>  
> +	ret = vfio_pci_zdev_reset(vdev);
> +	if (ret && ret != -ENODEV)
> +		return ret;
> +
>  	ret = pci_try_reset_function(vdev->pdev);
>  	up_write(&vdev->memory_lock);

You're going to be very unhappy if this lock isn't released.

>  
> diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
> index a9972eacb293..5288577b3170 100644
> --- a/drivers/vfio/pci/vfio_pci_priv.h
> +++ b/drivers/vfio/pci/vfio_pci_priv.h
> @@ -86,6 +86,7 @@ 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);
> +int vfio_pci_zdev_reset(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)
> @@ -100,6 +101,10 @@ static inline int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
>  
>  static inline void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
>  {}
> +int vfio_pci_zdev_reset(struct vfio_pci_core_device *vdev)
> +{
> +	return -ENODEV;
> +}
>  #endif
>  
>  static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
> index 818235b28caa..dd1919ccb3be 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -212,6 +212,45 @@ static int vfio_pci_zdev_setup_err_region(struct vfio_pci_core_device *vdev)
>  	return ret;
>  }
>  
> +int vfio_pci_zdev_reset(struct vfio_pci_core_device *vdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +	int rc = -EIO;
> +
> +	if (!zdev)
> +		return -ENODEV;
> +
> +	/*
> +	 * If we can't get the zdev->state_lock the device state is
> +	 * currently undergoing a transition and we bail out - just
> +	 * the same as if the device's state is not configured at all.
> +	 */
> +	if (!mutex_trylock(&zdev->state_lock))
> +		return rc;
> +
> +	/* We can reset only if the function is configured */
> +	if (zdev->state != ZPCI_FN_STATE_CONFIGURED)
> +		goto out;
> +
> +	rc = zpci_hot_reset_device(zdev);
> +	if (rc != 0)
> +		goto out;
> +
> +	if (!vdev->pci_saved_state) {
> +		pci_err(vdev->pdev, "No saved available for the device");
> +		rc = -EIO;
> +		goto out;
> +	}
> +
> +	pci_dev_lock(vdev->pdev);
> +	pci_load_saved_state(vdev->pdev, vdev->pci_saved_state);
> +	pci_restore_state(vdev->pdev);
> +	pci_dev_unlock(vdev->pdev);
> +out:
> +	mutex_unlock(&zdev->state_lock);
> +	return rc;
> +}

This looks like it should be a device or arch specific reset
implemented in drivers/pci, not vfio.  Thanks,

Alex

> +
>  int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
>  {
>  	struct zpci_dev *zdev = to_zpci(vdev->pdev);