Re: [PATCH 14/21] MIPS: KVM: Add nanosecond count bias KVM register

Paolo Bonzini
2014-05-28T16:24:04Z

Il 28/05/2014 16:21, James Hogan ha scritto:
> The implementation in QEMU that I've settled upon makes do with just
> COUNT_CTL and COUNT_RESUME, but with a slight kernel modification so
> that COUNT_RESUME is writeable (to any positive monotonic nanosecond
> value <= now). It works fairly cleanly and correctly even with stopping
> and starting VM clock (gdb, stop/cont, savevm/loadvm, live migration),
> to match the behaviour of the existing mips cpu timer emulation, so I
> plan to drop this bias patch, and will post a v2 patchset soon with just
> a few modifications.

It makes sense to have writable registers in the emulator, even if they
are read-only in real hardware. We also do that for x86, FWIW.

So the idea looks okay to me.

Paolo