On 2020-05-18 07:58, Anastassios Nanos wrote:
To spawn KVM-enabled Virtual Machines on Linux systems, one has to use
QEMU, or some other kind of VM monitor in user-space to host the vCPU
threads, I/O threads and various other book-keeping/management
mechanisms.
This is perfectly fine for a large number of reasons and use cases: for
instance, running generic VMs, running general purpose Operating
systems
that need some kind of emulation for legacy boot/hardware etc.
What if we wanted to execute a small piece of code as a guest instance,
without the involvement of user-space? The KVM functions are already
doing
what they should: VM and vCPU setup is already part of the kernel, the
only
missing piece is memory handling.
With these series, (a) we expose to the Linux Kernel the bare minimum
KVM
API functions in order to spawn a guest instance without the
intervention
of user-space; and (b) we tweak the memory handling code of KVM-related
functions to account for another kind of guest, spawned in
kernel-space.
PATCH #1 exposes the needed stub functions, whereas PATCH #2 introduces
the
changes in the KVM memory handling code for x86_64 and aarch64.
An example of use is provided based on kvmtest.c
[https://lwn.net/Articles/658512/] at
https://github.com/cloudkernels/kvmmtest
You don't explain *why* we would want this. What is the overhead of
having
a userspace if your guest doesn't need any userspace handling? The
kvmtest
example indeed shows that the KVM userspace API is usable without any
form
of emulation, hence has almost no cost.
Without a clear description of the advantages of your solution, as well
as a full featured in-tree use case, I find it pretty hard to support
this.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
