Re: [PATCH] cpu: Add starts_halted() method

[Peter Maydell]

On Wed, 8 Jul 2020 at 16:25, Eduardo Habkost <ehabkost@redhat.com> wrote:
> On Wed, Jul 08, 2020 at 02:14:03PM +0100, Peter Maydell wrote:
> > The original bug as described in the commit message sounds
> > to me like something we should look to fix in the implementation
> > of async_run_on_cpu() -- it shouldn't cause a CPU that's halfway
> > through reset to do a KVM_RUN or otherwise run guest code,
> > whether that CPU is going to start powered-up or powered-down.
>
> What "halfway through reset" means, exactly?  Isn't halted==1
> enough to indicate the CPU is in that state?

I mean "while we're in the middle of the CPU method that's
called by cpu_reset()". "halted==1" says "the CPU is halted";
that's not the same thing. KVM_RUN happening
as a side effect in the middle of that code is a bug
whether the CPU happens to be intended to be put into the
halted state or not. If the CPU is intended to be created
not-halted then KVM_RUN can happen after cpu reset
completes, but not before.

thanks
-- PMM