Bochs/bochs/plex86/TODO
Kevin Lawton 0768d01522 Added plex86 directory to bochs. This directory contains the
new experimental stripped-down version of plex86, which is now
  a user-code-only VM.  I ripped out all the fancy stuff in plex86,
  such that under that right conditions, user-code (protection level 3)
  can run at near native speeds inside the plex86 VM.
The general idea is that bochs emulates all the initial real-mode code,
  and guest kernel code (protection level 0).  When it senses the
  right conditions (like the context switches to user-code), a shim
  is called to execute the guest inside the plex86 VM.  All guest-generated
  faults/exceptions are then forwarded back to bochs to be handled in
  the emulator.
Actually, I'm not yet adding the mods to the bochs code (other than
  the shim code which is in a separate file), until I hear that we're
  back in a more development mode with bochs after the 2.0 release.
The plex86 subdirectory is really a separate project.  It's just more
  convenient to co-develop it with bochs for now.  Both projects are
  currently LGPL, but each should be taken to be a separate project,
  and have their own license file.  Plex86 (it's only a kernel driver
  now) could ultimately be used with other projects, as it's modular.
  I talked with Bryce, and we both agreed it's OK to keep plex86 as
  a subdir in bochs for now.
2003-01-01 17:32:06 +00:00

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Synchronize page writes with iCache in bochs.
Deal with cycle counts of guest execution in VM, and in
bochs/plex86 shim.
Complete the CPUID info passing between bochs/plex86.
Make a host-null.c file to demonstrate/test the OS-specific
files that are needed for a host port.
Deal with page_usage. How do we update this between timeslices?
Do we always clear it? Maybe we should keep a log of things to
clear (page_usage, GDT entries, PDE entries, ...) and clear those
before returning to user space.
monpanic breaks up into 2 monprints which hit user space twice.
Task segment must be a 32-bit'er.
Save/restore floating point state of host/VM.
pack guest_cpu_t structure.
deduct off some cycles for the IRET/int sequence.
Delete use of vm->addr, and split print-nexus into parts so we can
use direct host or guest fields. I don't like having implicit
pointer usage.
Not compiled for debug
Compiled for BX_SMP_PROCESSORS == 1
cpuid match
x86 host
monitor uses slots 1,2,3 so guest ring3 should not
use these slots.
FIX a20 in system fields.
FIX use of CPL in paging-mon.c. We can eliminate any
code other than CPL==3.
==================== From previous plex86 TODO file ====================
This is a list of the major tasks/achievements/milestones yet to-do.
We should keep this list prioritized, creating sort of a road map.
Hopefully, this will reduce duplicate suggestions on the developers
channels, and let people know where we are in the development process.
Entries listed first have highest priority.
<NEAR-TERM>
- Fix plex86 on Linux 2.4.x/SMP or with 1P and LAPIC enabled.
- Save FPU state on host <--> monitor context switch.
- Special guest-specific drivers and special emulated pseudo-devices
for faster graphics/network/disk access.
- Allow some of the inactive guest pages be host swappable.
Currently, all pages are locked down.
- Many performance enhancements (see PERFORMANCE)
- Test and get more guests running; list in 'GUESTS'.
- Allow memory to be mapped anywhere in the physical address
space.
- Allow certain guest pages to be swap eligible by the host.
This means they will have to be unavailable by the guest
during that time. Need a dynamic algorith for this.
- Test on 2.4 with SMP/APIC enabled on single processor machine.
- Deal with guest use of TF.
- Deal with LDT
Use monitor unmapped IO port handler rather than user space.
Get rid of VM message count instrumentation spew to kernel log
unallocVmPages/unreserve_guest_pages called twice,
release & teardown.
move mapMonitor to -host.c
Zero out GDT when remapped.
When is mapMonitor called?
Fix extra PDBR reload in nexus.S