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

[Eduardo Habkost <ehabkost@redhat.com>]

On Fri, Jul 10, 2020 at 05:02:38PM -0300, Thiago Jung Bauermann wrote:
> 
> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> 
> > On 7/9/20 5:26 AM, Thiago Jung Bauermann wrote:
> >>
> >> Thiago Jung Bauermann <bauerman@linux.ibm.com> writes:
> >>
> >>> I'm seeing the vcpu being KVM_RUN'd too early twice during hotplug.
> >>> Both of them are before cpu_reset() and ppc_cpu_reset().
> >>
> >> Hm, rereading the message obviously the above is partially wrong. The
> >> second case happens during ppc_cpu_reset().
> >>
> >>> Here's the second:
> >>>
> >>> #0  in qemu_cpu_kick_thread ()
> >>> #1  in qemu_cpu_kick ()
> >>> #2  in queue_work_on_cpu ()
> >>> #3  in async_run_on_cpu ()
> >>> #4  in tlb_flush_by_mmuidx ()
> >>> #5  in tlb_flush ()
> >>> #6  in ppc_tlb_invalidate_all ()
> >>> #7  in ppc_cpu_reset ()
> >>> #8  in device_transitional_reset ()
> >>> #9  in resettable_phase_hold ()
> >>> #10 in resettable_assert_reset ()
> >>> #11 in device_set_realized ()
> >
> > Dunno if related, might be helpful:
> > https://www.mail-archive.com/qemu-devel@nongnu.org/msg686477.html
> 
> Yes, it's helpful. Thanks!
> 
> So is was it resolved whether it's appropriate to do a cpu_reset()
> within realize?
> 
> Is the core of the problem that device_set_realize() ends up calling
> ppc_cpu_reset()?

There are 15 realize functions which call cpu_reset(), currently.
Making it safe seems more appropriate than forbidding it.

-- 
Eduardo