GSoC 2017: Xenbus_dmaGrantHandler Status report

[VAIBHAV GAUTAM]

Dear All,

I am Vaibhav Gautam, one of the participants of the Google Summer of Code
2017 involved with FreeBSD. The title of my project is "*Importing grant
table bus_dma(9) handler from OpenBSD to FreeBSD.*" The status report of my
work is as follows:

*Project Overview*
Grant tables are a mechanism for sharing and transferring frames between
domains, without requiring the participating domains to be privileged. The
OpenBSD has integrated grant reference into it bus_dma(9) subsystem. The
aim of the project to import the bus_dma(9) grant table handler from
OpenBSD to FreeBSD.

*Midterm Deliverable*
Have a Xen specific implementation of bus_dma(9) in order to map and share
grants with domains.

*Key Learnings*
1. Concepts of virtualization
2. Kernel debugging
3. Writing device drivers
4. Xen hypervisor
5. bus_dma (9) APIs

*Current Status*
The current status is that the grant table has been integrated with the
bus_dma structure. The DMA maps are being created to map physical addresses
of map segments to the grant table references. The implementation needs to
be further improved performance wise and to be extended to other functions
utilizing bus_dma. Also, to be fully integrated with all frontends and
backends present in FreeBSD.

*Files modified*
1. /usr/src/sys/x86/x86/busdma_bounce.c
2. /usr/src/sys/dev/xen/grant_table/grant_table.c
3. /usr/src/sys/xen/gnttab.h

For detailed info regarding the project, please refer to
https://wiki.freebsd.org/SummerOfCode2017/Xenbus_dmaGrantHandler.


Regards,
Vaibhav Gautam.