Re: [PATCH 2/4] reset: Add RESET_TYPE_WAKEUP

[Juraj Marcin]

On Thu, Aug 8, 2024 at 2:18 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Tue, 6 Aug 2024 at 17:08, Juraj Marcin <jmarcin@redhat.com> wrote:
> >
> > Some devices need to distinguish cold start reset from waking up from a
> > suspended state. This patch adds new value to the enum, and updates the
> > i386 wakeup method to use this new reset type.
> >
> > Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
> > ---
> >  docs/devel/reset.rst    | 7 +++++++
> >  hw/i386/pc.c            | 2 +-
> >  include/hw/resettable.h | 2 ++
> >  3 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/docs/devel/reset.rst b/docs/devel/reset.rst
> > index 9746a4e8a0..30c9a0cc2b 100644
> > --- a/docs/devel/reset.rst
> > +++ b/docs/devel/reset.rst
> > @@ -44,6 +44,13 @@ The Resettable interface handles reset types with an 
> > enum ``ResetType``:
> >    value on each cold reset, such as RNG seed information, and which they
> >    must not reinitialize on a snapshot-load reset.
> >
> > +``RESET_TYPE_WAKEUP``
> > +  This type is used when the machine is woken up from a suspended state 
> > (deep
> > +  sleep, suspend-to-ram). Devices that must not be reset to their initial 
> > state
> > +  after wake-up (for example virtio-mem) can use this state to 
> > differentiate
> > +  cold start from wake-up can use this state to differentiate cold start 
> > from
> > +  wake-up.
>
> I feel like this needs more clarity about what this is, since
> as a reset type it's a general behaviour, not a machine
> specific one. What exactly is "wakeup" and when does it happen?
> How does it differ from what you might call a "warm" reset,
> where the user pressed the front-panel reset button?
> Why is virtio-mem in particular interesting here?

Thank you for the feedback!

I have rewritten the paragraph:

This type is called for a reset when the system is being woken up from
a suspended state using the ``qemu_system_wakeup()`` function. If the
machine type needs to reset in its ``MachineClass::wakeup()`` method,
this reset type should be used so that devices can differentiate
system wake-up from other reset types. For example, a virtio-mem
device must not unplug its memory during wake-up, as that would clear
the guest RAM.

Is it clearer? Thank you!

>
> thanks
> -- PMM
>

--

Juraj Marcin