Re: [RFC v2 0/2] kvm: Use host timekeeping in guest.

[Suleiman Souhlal]

On Thu, Oct 10, 2019 at 7:39 PM Roman Kagan <rkagan@xxxxxxxxxxxxx> wrote:
>
> I wonder how feasible it is to map the host's vdso into the guest and
> thus make the guest use the *same* (as opposed to "synchronized") clock
> as the host's userspace?  Another benefit is that it's essentially an
> ABI so is not changed as liberally as internal structures like
> timekeeper, etc.  There is probably certain complication in handling the
> syscall fallback in the vdso when used in the guest kernel, though.
>
> You'll also need to ensure neither tsc scaling and nor offsetting is
> applied to the VM once this clock is enabled.

That is what I initially wanted to do, but I couldn't find an easy way
to map a host page into the guest, outside of the regular userspace
(ioctl) KVM way of adding memory to a VM.

-- Suleiman