TODO
From KVM
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