Re: [RFC PATCH v2 1/3] vfio: Use capability chains to handle device specific irq

[Zhenyu Wang <zhenyuw@linux.intel.com>]

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On 2019.06.04 17:55:32 +0800, Tina Zhang wrote:
> Caps the number of irqs with fixed indexes and uses capability chains
> to chain device specific irqs.
> 
> VFIO vGPU leverages this mechanism to trigger primary plane and cursor
> plane page flip event to the user space.
> 
> Signed-off-by: Tina Zhang <tina.zhang@intel.com>
> ---
>  include/uapi/linux/vfio.h | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 02bb7ad6e986..9b5e25937c7d 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -444,11 +444,31 @@ struct vfio_irq_info {
>  #define VFIO_IRQ_INFO_MASKABLE		(1 << 1)
>  #define VFIO_IRQ_INFO_AUTOMASKED	(1 << 2)
>  #define VFIO_IRQ_INFO_NORESIZE		(1 << 3)
> +#define VFIO_IRQ_INFO_FLAG_CAPS		(1 << 4) /* Info supports caps */
>  	__u32	index;		/* IRQ index */
> +	__u32	cap_offset;	/* Offset within info struct of first cap */
>  	__u32	count;		/* Number of IRQs within this index */

This would break ABI for get irq info. I think irq cap chain can just follow
vfio_irq_info.

>  };
>  #define VFIO_DEVICE_GET_IRQ_INFO	_IO(VFIO_TYPE, VFIO_BASE + 9)
>  
> +/*
> + * The irq type capability allows irqs unique to a specific device or
> + * class of devices to be exposed.
> + *
> + * The structures below define version 1 of this capability.
> + */
> +#define VFIO_IRQ_INFO_CAP_TYPE      3
> +
> +struct vfio_irq_info_cap_type {
> +	struct vfio_info_cap_header header;
> +	__u32 type;     /* global per bus driver */
> +	__u32 subtype;  /* type specific */
> +};
> +
> +#define VFIO_IRQ_TYPE_GFX				(1)
> +#define VFIO_IRQ_SUBTYPE_GFX_PRI_PLANE_FLIP		(1)
> +#define VFIO_IRQ_SUBTYPE_GFX_CUR_PLANE_FLIP		(2)
> +

Really need to split for different planes? I'd like a VFIO_IRQ_SUBTYPE_GFX_DISPLAY_EVENT
so user space can probe change for all.

>  /**
>   * VFIO_DEVICE_SET_IRQS - _IOW(VFIO_TYPE, VFIO_BASE + 10, struct vfio_irq_set)
>   *
> @@ -550,7 +570,8 @@ enum {
>  	VFIO_PCI_MSIX_IRQ_INDEX,
>  	VFIO_PCI_ERR_IRQ_INDEX,
>  	VFIO_PCI_REQ_IRQ_INDEX,
> -	VFIO_PCI_NUM_IRQS
> +	VFIO_PCI_NUM_IRQS = 5	/* Fixed user ABI, IRQ indexes >=5 use   */
> +				/* device specific cap to define content */
>  };
>  
>  /*
> -- 
> 2.17.1
> 

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