g2k16 Hackathon Report: Mike Larkin on vmm + vmd progress
Contributed by pitrh on Mon Sep 5 10:16:10 2016 (GMT)
from the virtually puffed dept.
The first developer report from the just concluded g2k16 hackathon comes from Mike Larkin, who writes:
I worked on vmm/vmd. I had been sitting on a diff since Nantes that implements a
real interrupt controller. This is so that we can have real hardclock
interrupts and avoid the previous clock hack that made vmd(8) spin at 100% CPU
Once I had that done, I cleaned up and refactored some vmd code, separating out
each device into its own module/file. This made it easier for stefan@ to add
asynchronous interrupt handling via libevent later in the week.
I next fixed the MSR (model specific register) bitmap. This is a giant mask
that tells the processor which MSRs to allow the guest VM direct access to. Some
are safe, some aren't, and some don't make sense at all in a VM. This bitmap
is now locked down to just the minimial set of MSRs needed for well-behaved
guest VMs (and those that aren't well behaved will think they are accessing
off-limits MSRs but we just discard writes and return 0s on read).
I also removed some CPUID feature bits exposed to guest VMs, again removing
things that aren't implemented or don't make sense in the guest VM (like the
various thermal management/speedstep bits).
I wrapped up the week by dusting off my diff to provide a real BIOS inside the
guest VM, that will make it easier to boot other types of guests by not
having to go through vmd's ELF bootloader. This last bit did not get completed,
and that's what I'm working on now.
Thanks to the organizers avsm and Gemma, it was a fun week.
Thanks for the report and all the awsome work on the virtualization system, Mike!
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