Re: [Qemu-devel] RFC [v2]: vfio / device assignment -- layout of device fd files

[Stuart Yoder]

>
> The other obvious possibility is a pure ioctl interface.  To match what
> this proposal is trying to describe, plus the runtime interfaces, we'd
> need something like:
>
> /* :0 - PCI devices, :1 - Devices path device, 63:2 - reserved */
> #define VFIO_DEVICE_GET_FLAGS                   _IOR(, , u64)
>
>
> /* Return number of mmio/iop/config regions.
>  * For PCI this is always 8 (BAR0-5 + ROM + Config) */
> #define VFIO_DEVICE_GET_NUM_REGIONS             _IOR(, , int)
>
> /* Return length for region index (may be zero) */
> #define VFIO_DEVICE_GET_REGION_LEN              _IOWR(, , u64)
>
> /* Return flags for region index
>  * :0 - mmap'able, :1 - read-only, 63:2 - reserved */
> #define VFIO_DEVICE_GET_REGION_FLAGS            _IOR(, , u64)
>
> /* Return file offset for region index */
> #define VFIO_DEVICE_GET_REGION_OFFSET           _IOWR(, , u64)
>
> /* Return physical address for region index - not implemented for PCI */
> #define VFIO_DEVICE_GET_REGION_PHYS_ADDR        _IOWR(, , u64)
>
>
>
> /* Return number of IRQs (Not including MSI/MSI-X for PCI) */
> #define VFIO_DEVICE_GET_NUM_IRQ                 _IOR(, , int)
>
> /* Set IRQ eventfd for IRQ index, arg[0] = index, arg[1] = fd */
> #define VFIO_DEVICE_SET_IRQ_EVENTFD             _IOW(, , int)
>
> /* Unmask IRQ index */
> #define VFIO_DEVICE_UNMASK_IRQ                  _IOW(, , int)
>
> /* Set unmask eventfd for index, arg[0] = index, arg[1] = fd */
> #define VFIO_DEVICE_SET_UNMASK_IRQ_EVENTFD      _IOW(, , int)
>
>
> /* Return the device tree path for type/index into the user
>  * allocated buffer */
> struct dtpath {
>        u32     type; (0 = region, 1 = IRQ)
>        u32     index;
>        u32     buf_len;
>        char    *buf;
> };
> #define VFIO_DEVICE_GET_DTPATH                  _IOWR(, , struct dtpath)
>
> /* Return the device tree index for type/index */
> struct dtindex {
>        u32     type; (0 = region, 1 = IRQ)
>        u32     index;
>        u32     prop_type;
>        u32     prop_index;
> };
> #define VFIO_DEVICE_GET_DTINDEX                 _IOWR(, , struct dtindex)
>
>
> /* Reset the device */
> #define VFIO_DEVICE_RESET                       _IO(, ,)
>
>
> /* PCI MSI setup, arg[0] = #, arg[1-n] = eventfds */
> #define VFIO_DEVICE_PCI_SET_MSI_EVENTFDS        _IOW(, , int)
> #define VFIO_DEVICE_PCI_SET_MSIX_EVENTFDS       _IOW(, , int)
>
> Hope that covers it.  Something I prefer about this interface is that
> everything can easily be generated on the fly, whereas reading out a
> table from the device means we really need to have that table somewhere
> in kernel memory to easily support reading random offsets.  Thoughts?

I think this could work, but I'm not sure it makes the problem David
had any better--  you substitute the complexity of parsing the
variable length regions with invoking a set of APIs.

Stuart