Tuesday, September 25, 2012

I'm back

So I've decided I should continue to write here. After all, I work on relatively interesting, exciting to me things I feel I need to share with the world :-).


It's been an interesting summer. After attending the Linux Symposium in Ottawa with three papers [0] and being again a Tiano Core mentor for Google Summer of Code, I'm back to hacking things filesystem and virtualization related.

My Xen port to Tegra2 has been seeing a lot of attention from me. It's hard to call it a port, as I'm mostly approaching it from rewrite-everything angle, especially given the research prototype status of the initial Samsung ARMv5 tree I forked over two years ago. Of course, EmbeddedXen and ARM PV efforts haven't been sitting still in the meantime, but I'm treating the project as a personal "let's write a hypervisor" effort. There's no explicit desire to be compatible to any other ARM Xen effort.

My branch is targetting ARMv7, initially since that's what I've got around the house, but after digging through ARM ARM both for v6 and v7 I'm glad I'm not targeting anything older. The current differences from the original Samsung tree -
* ARMv7-only support.
* Tegra2 platform, targeting the Motorola Xoom
* Dom0/U configuration is not hardcoded.
* Boot through ATAG-compatible bootloader, with all images passed through a "boot volume".
* Kernel threads ("xen domains"), which are currently cooperative, but full preemption is a design goal.
* No ACM, given likely hypercall changes.
* A FIQ-based extensible serial kernel debugger with useful commands to help debugging and bring-up.
* In progress work on a framebuffer debug console.
* Reworked VMM and PT support with AFE and XN.

I'm concentrating on fleshing out crash debugging and framebuffer debug console support at the moment. After that it's (in no particular order) -
* L2 cache integration.
* Synchronization.
* Switching to VM and back.
* Full preemption for xen domains.
* Hypercall definitions.

I'll leave you with a short video demonstration of what I've got at the moment. It's not too amazing, the most interesting stuff is well ahead.

[0] http://labs.vmware.com/publications/2012-linux-symposium-publications
[1] https://github.com/andreiw/xen3-arm-tegra

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