Re: [PATCH 1/5] hw/ppc/spapr_iommu: Register machine reset handler

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Apr 27, 2021 at 11:20:07AM +0200, Philippe Mathieu-Daudé wrote:
> On 4/27/21 3:45 AM, David Gibson wrote:
> > On Sat, Apr 24, 2021 at 06:22:25PM +0200, Philippe Mathieu-Daudé wrote:
> >> The TYPE_SPAPR_TCE_TABLE device is bus-less, thus isn't reset
> >> automatically.  Register a reset handler to get reset with the
> >> machine.
> >>
> >> It doesn't seem to be an issue because it is that way since the
> >> device QDev'ifycation 8 years ago, in commit a83000f5e3f
> >> ("spapr-tce: make sPAPRTCETable a proper device").
> >> Still, correct to have a proper API usage.
> > 
> > So, the reason this works now is that we explicitly call
> > device_reset() on the TCE table from the TCE tables "owner", either a
> > PHB (spapr_phb_reset()) or a VIO device (spapr_vio_quiesce_one()).
> > 
> > I think we want either that, or the register_reset(), not both.
> 
> rtas_quiesce() seems to call a DeviceClass::reset() on the
> children of TYPE_SPAPR_VIO_BUS:
> 
> Abstract TYPE_VIO_SPAPR_DEVICE has the TYPE_SPAPR_VIO_BUS bus_type,
> and registers the spapr_vio_busdev_reset() handler, which calls
> spapr_vio_quiesce_one()...
> 
> So either we already have 2 resets, or the bus is never reset?

There are 2 resets, and this is intentional.  We reset once at machine
reset time, via the bus.  Once a booting OS is done with the firmware
it calls "quiesce" to put all the devices back into a safe state.  The
easiest way to do that is just to invoke their reset callbacks, so
that's what we do.

> The bus is created in spapr_machine_init():
> 
>     /* Set up VIO bus */
>     spapr->vio_bus = spapr_vio_bus_init();
> 
> TYPE_SPAPR_MACHINE class registers spapr_machine_reset(), which
> manually calls qemu_devices_reset() and spapr_drc_reset_all(),
> but I can't understand if a callee resets vio_bus...
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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