[GSOC] Implement hardware nested page table support for vkernels

Chris Turner c.turner at 199technologies.com
Mon Apr 29 18:32:39 PDT 2013

On 04/28/13 03:28, Mihai Carabas wrote:
> Here is my official application for GSoC 2013 [1] (it's public). Any comments/reviews are welcome.

- Probably a basic introductory paragraph r.e. what a vkernel actually is might be useful
   to set context. Ditto r.e. references to the vmspace() api. I've not worked with GSOC
   people, so maybe this is a bad suggestion - Justin probably has more to say about this :D

- When I had pointed out v3vee/bhyve I had confused 'nested page tables'
   w/ 'virtualization extensions', thinking you were planning on extending vkernel
   to use vt-x. Using NPT directly from the host as a virtualization assist is pretty
   nifty actually and might actually be something novel on x86 (not sure if LxC or
   Solaris Zones, yadda are using these) In any event - apologies for any
   confusion here.

- One of the bottlenecks in the current vkernel implementation is for IO -
   Previous VKernel internals used virtual-upcalls to manage IO, which IIRC is now
   done through a host-side dedicated IO pthread. Time / interest permitting,
   it might be worthwhile to review if NPT and some kind of host:guest
   cooperation could also be beneficial for IO in addition to memory,
   and also if the now-present support for 'virtio' could be
   leveraged in some manner here (I'm not up on how virtio works).
   But that could easily be a 'follow up project'

Cheers & Good Luck!

- Chris

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