linux-kernel - Re: [PATCH v7 7/9] vfio-pci/zdev: Add a device feature for error information

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Message-Id: <DFSPESVR3INE.HYERH8O05PYP@linux.ibm.com>
Date: Mon, 19 Jan 2026 17:24:53 +0100
From: "Julian Ruess" <julianr@...ux.ibm.com>
To: "Farhan Ali" <alifm@...ux.ibm.com>, <linux-s390@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Cc: <helgaas@...nel.org>, <lukas@...ner.de>, <alex@...zbot.org>,
        <clg@...hat.com>, <stable@...r.kernel.org>, <schnelle@...ux.ibm.com>,
        <mjrosato@...ux.ibm.com>
Subject: Re: [PATCH v7 7/9] vfio-pci/zdev: Add a device feature for error
 information

On Wed Jan 7, 2026 at 7:32 PM CET, Farhan Ali wrote:
> For zPCI devices, we have platform specific error information. The platform
> firmware provides this error information to the operating system in an
> architecture specific mechanism. To enable recovery from userspace for
> these devices, we want to expose this error information to userspace. Add a
> new device feature to expose this information.
>
> Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c |  2 ++
>  drivers/vfio/pci/vfio_pci_priv.h |  9 +++++++++
>  drivers/vfio/pci/vfio_pci_zdev.c | 34 ++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h        | 16 +++++++++++++++
>  4 files changed, 61 insertions(+)
>
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 3a11e6f450f7..f677705921e6 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1526,6 +1526,8 @@ int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags,
>  		return vfio_pci_core_feature_token(vdev, flags, arg, argsz);
>  	case VFIO_DEVICE_FEATURE_DMA_BUF:
>  		return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz);
> +	case VFIO_DEVICE_FEATURE_ZPCI_ERROR:
> +		return vfio_pci_zdev_feature_err(device, flags, arg, argsz);

Would it make sense to name this more generically, e.g.
VFIO_DEVICE_FEATURE_ERROR_RECOVERY, in case other architectures also want to
support something like this in the future?

-- snip --

>  
>  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 2be37eab9279..261954039aa9 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -141,6 +141,40 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
>  	return ret;
>  }
>  
> +int vfio_pci_zdev_feature_err(struct vfio_device *device, u32 flags,
> +			      void __user *arg, size_t argsz)
> +{
> +	struct vfio_device_feature_zpci_err err;
> +	struct vfio_pci_core_device *vdev =
> +		container_of(device, struct vfio_pci_core_device, vdev);
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +	int ret;
> +	int head = 0;

Maybe we should use reverse x-mas notation:
	struct vfio_device_feature_zpci_err err;
	struct vfio_pci_core_device *vdev;
	struct zpci_dev *zdev;
	int head = 0;
	int ret;

	vdev = container_of(device, struct vfio_pci_core_device, vdev);
	zdev = to_zpci(vdev->pdev);

-- snip --