TODO

TODO

---

The following items need some love. Please post to the list if you are interested in helping out:

• Real mode support: VT support for real mode is terrible, so we need to do it in software. This means extending the x86 emulator (x86_emulate.c) to handle more instructions, and changing the execution loop to call the emulator for real mode (in progress).
• Move the apic/ioapic/pic/pit emulation into the kernel. This will simplify in-kernel paravirtualized devices (as there is no need to exit to userspace to inject an interrupt) and guest SMP (in progress).
• Drop the preemption counter while doing mmu stuff, and turn kvm->lock into a mutex.
  • Even better, hook the state switch to the scheduler, and do away with disabling preemption completely (in progress).
• Emulate the architectural performance monitor counters/msrs, for Linux nmi watchdog support.

The following smaller scale tasks can be a nice entry point to someone wishing to get involved:

• Enforce the virtual time stamp counter monotonicity even when a vcpu is migrated to another physical cpu. (done for AMD, in progress for Intel)
• Trap #UD and emulate sysenter/syscall/sysret/sysexit. These instructions don't exist on all cpus in all modes, so they hinder cross-vendor migration (in progress)
• Consolidate the inb/outb emulation helpers into x86_emulate.c
• Store command line options in an empty snapshot in a qcow2 format image file. This allows an image file to be self contained: qemu file.img should be enough to launch a fully configured virtual machine.

MMU related:

• Attach kvm memory to a Linux address_space so that guest memory can be paged out (patch exists for alternative approach to guest paging).
• Support large pages (in conjunction with the item above) so that if the guest uses a large page mapping and the guest memory is backed by hugetlbfs, a large-page pte is created.
• Improve mmu page eviction algorithm (currently FIFO, change to approximate LRU).
• Add a read-only memory type.
• Implement AM20 for dos and the like.
• Implement direct page tables on paravirt_ops enabled Linux guests (in progress)

x86 emulator updates:

• Currently, the emulator is called twice for each instruction that reads mmio memory: once to fetch the operand

  and once to execute.  Split the emulator into two functions: one to decode into the emulation context, and
  the other to actually execute the instruction.

For the adventurous:

• Emulate the VT and SVM instructions, so that kvm can run in a virtual machine. Test by running a VM in a VT guest in an SVM guest on VT hardware, as well as running a VM in an SVM guest in a VT guest on SVM hardware.
• Emulate the VT and SVM instruction sets on qemu. This would be very beneficial to debugging kvm.
• Keep this TODO up to date