Grant Table Userspace Device - Status Update

[Akshay Jaggi]

Hello Everyone,

Hope everyone is doing great.

This is the last week of GSoC-2016, and the grant table userspace device is
complete. We are actively working to get the code reviewed and pushed.

Here is the list of patches in the pipeline:

   - https://reviews.freebsd.org/D7429
   - https://reviews.freebsd.org/D7293
   -
   https://lists.xenproject.org/archives/html/xen-devel/2016-08/msg02125.html

I'll be using this thread to discuss the overall progress of code-review
for all the three patches, and I hope that would be fine.

Looking forward to getting this stuff to mainline. :)

Regards,
Akshay

On 20 July 2016 at 20:33, Akshay Jaggi <akshay1994.leo at gmail.com> wrote:

> Hello Everyone,
>
>
> I hope everyone is doing great.
>
>
> First things first. I want to apologise for not updating my blogpost after
> June 15. Some personal stuff happened on June 17, and since then all my
> work routines are completely disturbed. Soc-admins know about this, and I
> hope the community can pardon my irregularity this once.
>
>
> Now, time for some status update on the project. We have a working Grant
> Table User-space Device (with some caveats, of course). Yay!!
>
> Check out the code on the pull request: https://github.com/
> freebsd/freebsd/compare/master...akshay1994:grant_table?expand=1
>
> Test the device by compiling a custom kernel; from my working branch:
> https://github.com/akshay1994/freebsd/tree/grant_table
>
>
> Caveats and work yet to be done:
>
>    - A kernel panic happens if you terminate the program without
>    un-mmapping all the mmaps.
>    - The interface for a grant map is not completely in sync with the
>    Linux interface yet. Notably, we still map and subsequently mmap partially
>    working grants. This is a bug since the pager will fail on a page fault for
>    the non-working-grant.
>    - I'm yet to add event channel code for the notify ioctls.
>    - I'm yet to get in touch with the vm-guys. I spent a lot of time
>    understanding the vm structure, but I surely do not have a complete
>    picture. I'm using a MGTDEVICE cdev pager to handle managed, fictitious
>    pages from mapped grants, and a custom PHYS vm object to manage wired
>    physical memory for allocated grants. I have to
>       - Confirm if the approach I am using is the best one.
>       - The interface differs compared to Linux with regards to multiple
>       mmaps, which I need a little help with.
>
>
> Looking forward to some community testing of the working parts.
> Comments are welcome and highly appreciated. :)
>
>
> Regards,
> Akshay Jaggi
>