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This code is ugly, but it's working.

Tested with basic module, and appears to be working
properly. I will soon incorporate the patched
modprobe into the kernel tree, and then this code
will be usable by everyone.

The ipc code is still unimplemented. The only
hypercall handled is yield. Also note that other
exit conditions (e.g. external interrupt) have not
been fully tested.

Overview:
-- kernel code calls lcd_create_as_module with
   the module's name
-- lcd_create_as_module loads the module using
   request_lcd_module (request_lcd_module calls
   the patched modprobe to load the module, and
   the patched modprobe calls back into the lcd
   driver via the ioctrl interface to load the
   module)
-- lcd_create_as_module then finds the loaded
   module, spawns a kernel thread and passes off
   the module to it
-- the kernel thread initializes the lcd and
   maps the module inside it, then suspends itself
-- lcd_run_as_module wakes up the kernel thread
   and tells it to run
-- lcd_delete_as_module stops the kernel thread
   and deletes the module from the host kernel

File-by-file details:

arch/x86/include/asm/lcd-domains-arch.h
arch/x86/lcd-domains/lcd-domains-arch-tests.c
arch/x86/lcd-domains/lcd-domains-arch.c
-- lcd was not running in 64-bit mode, and my
   checks had one subtle bug
-- fixed %cr3 load to properly load vmcs first
-- fixed set program counter to use guest virtual
   rather than guest physical address

include/linux/sched.h
-- added struct lcd to task_struct

include/linux/init_task.h
-- lcd pointer set to null when task_struct is
   initialized

include/linux/module.h
kernel/module.c
-- made init_module and delete_module system calls
   callable from kernel code
-- available in module.h via do_sys_init_module and
   do_sys_delete_module
-- simply moved the majority of the guts of the
   system calls into a non-system call, exported
   routine
-- take an extra flag, for_lcd; when set, the init
   code skips over running (and deallocating) the
   module's init code, and the delete code skips
   over running the module exit
-- system calls from user code set for_lcd = 0; this
   ensures existing code still works

include/linux/kmod.h
kernel/kmod.c
kernel/sysctl.c
-- changed __request_module to __do_request_module; takes
   one extra argument, for_lcd
-- __request_module   ==>  __do_request_module with for_lcd = 0
-- request_lcd_module ==>  __do_request_module with for_lcd = 1
-- call_modprobe conditionally uses lcd_modprobe_path, the path
   to a patched modprobe accessible via sysfs

include/lcd-domains/lcd-domains.h
-- added lcd status enum; see source code doc
-- three routines for creating/running/destroying
   lcd's that use modules; see source code doc

include/uapi/linux/lcd-domains.h
-- added interface defns for patched modprobe to call into
   lcd driver for module init; lcd driver loads
   module (via slightly refactored module.c code) on behalf
   of modprobe

virt/lcd-domains/lcd-domains.c
-- implementation of routines for modules inside lcd's
-- implementation of module init / delete for lcd's
   (uses patched module.c code)

virt/lcd-domains/Kconfig
virt/lcd-domains/Makefile
virt/lcd-domains/lcd-module-load-test.c
virt/lcd-domains/lcd-tests.c
-- added test module for lcd module code
-- test runs automatically when lcd module is inserted

In the process of debugging, major corrections and
debug checks implemented (this is a big squash):
-- coded up entry checks documented in Intel SDM
   V3 chp 26 (this should help later if settings
   are changed, make it less risky to experiment
   and give more confidence)
-- fixed host tr base addr bug (the worst bug! caused
   system to hang and then crash, since the tss
   was erroneous...)
-- fixed vmx_entry to properly set host rsp before
   entry
-- setting host sysenter and idt info
-- fixed cs ar bytes bug
-- fixed gdt limit bug
-- fixed tr type bug
-- extra settings added to cr0 and cr4, but may
   not be needed ... (debug fix attempt)
-- lstar mstar autoload, may not be needed ...
   (debug fix attempt)

Fixed (another) nasty casting bug in the
code that initializes the ept pointer. I
was using the old way of casting, and overlooking
that I was storing a host virtual pointer
inside a host physical pointer. This caused
invept to fail (invept checks if the eptp is
valid).

I also fixed invept and invvpid to print an
error message (like vmload and vmclear), rather
than generate an invalid opcode exception. It's
easier to debug and understand the problem.

In the future, we could more carefully parse the
error returned.

Nasty casting bug. (I should create separate
types for gpa, hpa, hva, gva...).

Updated tests.

Added pgd_pfn to asm/pgtables.h.

I needed to mask off the flags in the lower part
of the pte ...

For paging mem allocation.

Pushing in case of crash ...