Re: [Qemu-devel] [RFC PATCH v4 1/3] Mediated device Core driver

[Neo Jia <cjia@nvidia.com>]

On Mon, Jun 06, 2016 at 04:29:11PM +0800, Dong Jia wrote:
> On Sun, 5 Jun 2016 23:27:42 -0700
> Neo Jia <cjia@nvidia.com> wrote:
> 
> 2. VFIO_DEVICE_CCW_CMD_REQUEST
> This intends to handle an intercepted channel I/O instruction. It
> basically need to do the following thing:

May I ask how and when QEMU knows that he needs to issue such VFIO ioctl at
first place?

Thanks,
Neo

>   a. Copy the raw data of the CCW program (a group of chained CCWs) from
>      user into kernel space buffers.
>   b. Do CCW program translation based on the raw data to get a
>      real-device runnable CCW program. We'd pin pages for those CCWs
>      which have memory space pointers for their offload, and update the
>      CCW program with the pinned results (phys).
>   c. Issue the translated CCW program to a real-device to perform the
>      I/O operation, and wait for the I/O result interrupt.
>   d. Once we got the I/O result, copy the result back to user, and
>      unpin the pages.
> 
> Step c could only be done by the physical device driver, since it's it
> that the int_handler belongs to.
> Step b and d should be done by the physical device driver. Or we'd
> pin/unpin pages in the mediated device driver?
> 
> That's why I asked for the new callback.
>