Re: [PATCH 1/2] VFIO-AER: Vfio-pci driver changes for supporting AER

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On Wed, 2013-01-09 at 06:26 +0000, Pandarathil, Vijaymohan R wrote:
> 	- New ioctl which is used to pass the eventfd that is signaled when
>           an error occurs in the vfio_pci_device
> 
> 	- Register pci_error_handler for the vfio_pci driver
> 
> 	- When the device encounters an error, the error handler registered by
>           the vfio_pci driver gets invoked by the AER infrastructure
> 
> 	- In the error handler, signal the eventfd registered for the device.
> 
> 	- This results in the qemu eventfd handler getting invoked and
>           appropriate action taken for the guest.
> 
> Signed-off-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@xxxxxx>
> ---
>  drivers/vfio/pci/vfio_pci.c         | 29 +++++++++++++++++++++++++++++
>  drivers/vfio/pci/vfio_pci_private.h |  1 +
>  drivers/vfio/vfio.c                 |  8 ++++++++
>  include/linux/vfio.h                |  1 +
>  include/uapi/linux/vfio.h           |  9 +++++++++
>  5 files changed, 48 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 6c11994..4ae9526 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -207,6 +207,8 @@ static long vfio_pci_ioctl(void *device_data,
>  		if (vdev->reset_works)
>  			info.flags |= VFIO_DEVICE_FLAGS_RESET;
>  
> +		info.flags |= VFIO_DEVICE_FLAGS_AER_NOTIFY;
> +

This appears to be a PCI specific flag, so the name should include
_PCI_.  We also support non-PCIe devices and it seems like it would be
possible to not have AER support available, so shouldn't this be
conditional?

>  		info.num_regions = VFIO_PCI_NUM_REGIONS;
>  		info.num_irqs = VFIO_PCI_NUM_IRQS;
>  
> @@ -348,6 +350,19 @@ static long vfio_pci_ioctl(void *device_data,
>  
>  		return ret;
>  
> +	} else if (cmd == VFIO_DEVICE_SET_ERRFD) {
> +		int32_t fd = (int32_t)arg;
> +
> +		if (fd < 0)
> +			return -EINVAL;
> +
> +		vdev->err_trigger = eventfd_ctx_fdget(fd);
> +
> +		if (IS_ERR(vdev->err_trigger))
> +			return PTR_ERR(vdev->err_trigger);
> +
> +		return 0;
> +

I'm not sure why we wouldn't describe this as just another interrupt
from the device and configure it via SET_IRQ.  This ioctl has very
limited use and doesn't follow any of the conventions of all the other
vfio ioctls.

>  	} else if (cmd == VFIO_DEVICE_RESET)
>  		return vdev->reset_works ?
>  			pci_reset_function(vdev->pdev) : -EINVAL;
> @@ -527,11 +542,25 @@ static void vfio_pci_remove(struct pci_dev *pdev)
>  	kfree(vdev);
>  }
>  
> +static pci_ers_result_t vfio_err_detected(struct pci_dev *pdev,
> +				pci_channel_state_t state)
> +{
> +	struct vfio_pci_device *vdev = vfio_get_vdev(&pdev->dev);
> +
> +	eventfd_signal(vdev->err_trigger, 1);
> +	return PCI_ERS_RESULT_CAN_RECOVER;
> +}

What if err_trigger hasn't been set?

> +
> +static const struct pci_error_handlers vfio_err_handlers = {
> +	.error_detected = vfio_err_detected,
> +};
> +
>  static struct pci_driver vfio_pci_driver = {
>  	.name		= "vfio-pci",
>  	.id_table	= NULL, /* only dynamic ids */
>  	.probe		= vfio_pci_probe,
>  	.remove		= vfio_pci_remove,
> +	.err_handler	= &vfio_err_handlers,
>  };
>  
>  static void __exit vfio_pci_cleanup(void)
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index 611827c..daee62f 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -55,6 +55,7 @@ struct vfio_pci_device {
>  	bool			bardirty;
>  	struct pci_saved_state	*pci_saved_state;
>  	atomic_t		refcnt;
> +	struct eventfd_ctx	*err_trigger;
>  };
>  
>  #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 56097c6..5ed5a54 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -693,6 +693,14 @@ void *vfio_del_group_dev(struct device *dev)
>  }
>  EXPORT_SYMBOL_GPL(vfio_del_group_dev);
>  
> +void *vfio_get_vdev(struct device *dev)
> +{
> +	struct vfio_device *device = dev_get_drvdata(dev);
> +
> +	return device->device_data;
> +}
> +EXPORT_SYMBOL_GPL(vfio_get_vdev);
> +

This is unsafe.  How do we know dev is a vfio device?  How do we keep
that drvdata valid while you're using it?  I think you want to export
the existing vfio_group_get_device() and vfio_device_put().  Thanks,

Alex

>  /**
>   * VFIO base fd, /dev/vfio/vfio
>   */
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index ab9e862..3c97b03 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -45,6 +45,7 @@ extern int vfio_add_group_dev(struct device *dev,
>  			      void *device_data);
>  
>  extern void *vfio_del_group_dev(struct device *dev);
> +extern void *vfio_get_vdev(struct device *dev);
>  
>  /**
>   * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 4758d1b..fa67213 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -147,6 +147,7 @@ struct vfio_device_info {
>  	__u32	flags;
>  #define VFIO_DEVICE_FLAGS_RESET	(1 << 0)	/* Device supports reset */
>  #define VFIO_DEVICE_FLAGS_PCI	(1 << 1)	/* vfio-pci device */
> +#define VFIO_DEVICE_FLAGS_AER_NOTIFY (1 << 2)	/* Supports aer notify */
>  	__u32	num_regions;	/* Max region index + 1 */
>  	__u32	num_irqs;	/* Max IRQ index + 1 */
>  };
> @@ -288,6 +289,14 @@ struct vfio_irq_set {
>   */
>  #define VFIO_DEVICE_RESET		_IO(VFIO_TYPE, VFIO_BASE + 11)
>  
> +/**
> + * VFIO_DEVICE_SET_ERRFD - _IO(VFIO_TYPE, VFIO_BASE + 12)
> + *
> + * Pass the eventfd to the vfio-pci driver for signalling any device
> + * error notifications
> + */
> +#define VFIO_DEVICE_SET_ERRFD		_IO(VFIO_TYPE, VFIO_BASE + 12)
> +
>  /*
>   * The VFIO-PCI bus driver makes use of the following fixed region and
>   * IRQ index mapping.  Unimplemented regions return a size of zero.



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