RE: [RFC PATCH v3 1/4] vfio: Define device specific irq type capability

[Zhang, Tina]

> -----Original Message-----
> From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx]
> Sent: Thursday, June 27, 2019 12:08 PM
> To: Zhang, Tina <tina.zhang@xxxxxxxxx>
> Cc: intel-gvt-dev@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; kraxel@xxxxxxxxxx; zhenyuw@xxxxxxxxxxxxxxx; Lv,
> Zhiyuan <zhiyuan.lv@xxxxxxxxx>; Wang, Zhi A <zhi.a.wang@xxxxxxxxx>; Tian,
> Kevin <kevin.tian@xxxxxxxxx>; Yuan, Hang <hang.yuan@xxxxxxxxx>
> Subject: Re: [RFC PATCH v3 1/4] vfio: Define device specific irq type
> capability
> 
> On Thu, 27 Jun 2019 11:37:59 +0800
> Tina Zhang <tina.zhang@xxxxxxxxx> wrote:
> 
> > Cap the number of irqs with fixed indexes and use capability chains to
> > chain device specific irqs.
> >
> > Signed-off-by: Tina Zhang <tina.zhang@xxxxxxxxx>
> > ---
> >  include/uapi/linux/vfio.h | 19 ++++++++++++++++++-
> >  1 file changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 02bb7ad6e986..600784acc4ac 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -444,11 +444,27 @@ 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 cannot be inserted into the middle of the structure, it breaks
> compatibility with all existing userspace binaries.  I must be added to the end
> of the structure.
Indeed. Thanks.

BR,
Tina
> 
> >  #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 */
> > +};
> > +
> >  /**
> >   * VFIO_DEVICE_SET_IRQS - _IOW(VFIO_TYPE, VFIO_BASE + 10, struct
> vfio_irq_set)
> >   *
> > @@ -550,7 +566,8 @@ 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 */
> >  };
> >
> >  /*