This patchset is an incremental improvement to our reset handling that
tries to roll out the "three-phase-reset" design we have for devices
to a wider scope.
At the moment devices and buses have a three-phase reset system, with
separate 'enter', 'hold' and 'exit' phases. When the qbus tree is
reset, first all the devices on it have their 'enter' method called,
then they all have 'enter' called, and finally 'exit'. The idea is
that we can use this, among other things, as a way to resolve annoying
"this bit of reset work needs to happen before this other bit of reset
work" ordering issues.
However, there is still a "legacy" reset option, where you register a
callback function with qemu_register_reset(). These functions know
nothing about the three-phase system, and "reset the qbus" is just one
of the things set up to happen at reset via qemu_register_reset().
That means that a qemu_register_reset() function might happen before
all the enter/hold/exit phases of device reset, or it might happen after
all of them.
This patchset provides a new way to register a three-phase-aware reset
in this list of "reset the whole system" actions, and reimplements
qemu_register_reset() in terms of that new mechanism. This means that
qemu_register_reset() functions are now all called in the 'hold' phase
of system reset. (This is an ordering change, so in theory it could
introduce new bugs if we are accidentally depending on the current
ordering; but we have very few enter and exit phase methods at the
moment so I don't expect much trouble, if any.)
The first three patches remove the only two places in the codebase
that rely on "a reset callback can unregister itself within the
callback"; this is awkward to continue to support in the new
implementation, and an unusual thing to do given that reset is in
principle supposed to be something you can do as many times as you
like, not something that behaves differently the first time through.
Patch 4 is an improvement to the QOM macros that's been on list as an
RFC already.
Patches 5 and 6 are the "new mechanism": qemu_register_resettable()
takes any object that implements the Resettable interface. System
reset is then doing 3-phase reset on all of these, so everything
gets its 'enter' phase called, then everything gets 'hold', then
everything gets 'exit'.
Patch 7 reimplements the qemu_register_reset() API to be
"qemu_register_resettable(), and the callback function is called
in the 'hold' phase".
Patch 8 makes the first real use of the new API: instead of
doing the qbus reset via qemu_register_reset(), we pass the
root of the qbus to qemu_register_resettable(). (This is where
the ordering change I mention above happens, as device enter and
exit method calls will now happen before and after all the
qemu_register_reset() function callbacks, rather than in the
middle of them.)
Finally, patch 9 updates the developer docs to describe how a
complete system reset currently works.
This series doesn't actually do a great deal as it stands, but I
think it's a necessary foundation for some cleanups:
* the vfio reset ordering problem discussed on list a while back
should now hopefully be solvable by having the vfio code use
qemu_register_resettable() so it can arrange to do the "needs to
happen last" stuff in an exit phase method
* there are some other missing pieces here, but eventually I think
it should be possible to get rid of the workarounds for
dependencies between ROM image loading and CPUs that want to
read an initial PC/SP on reset (eg arm, m68k)
thanks
-- PMM
Peter Maydell (10):
hw/i386: Store pointers to IDE buses in PCMachineState
hw/i386/pc: Do pc_cmos_init_late() from pc_machine_done()
system/bootdevice: Don't unregister reset handler in
restore_boot_order()
include/qom/object.h: New OBJECT_DEFINE_SIMPLE_TYPE{,_WITH_INTERFACES}
macros
hw/core: Add documentation and license comments to reset.h
hw/core: Add ResetContainer which holds objects implementing
Resettable
hw/core/reset: Add qemu_{register,unregister}_resettable()
hw/core/reset: Implement qemu_register_reset via
qemu_register_resettable
hw/core/machine: Use qemu_register_resettable for sysbus reset
docs/devel/reset: Update to discuss system reset
MAINTAINERS | 10 ++
docs/devel/qom.rst | 34 ++++++-
docs/devel/reset.rst | 44 +++++++-
include/hw/core/resetcontainer.h | 48 +++++++++
include/hw/i386/pc.h | 4 +-
include/qom/object.h | 114 ++++++++++++++++-----
include/sysemu/reset.h | 113 +++++++++++++++++++++
hw/core/machine.c | 7 +-
hw/core/reset.c | 166 +++++++++++++++++++++++++------
hw/core/resetcontainer.c | 76 ++++++++++++++
hw/i386/pc.c | 40 +++-----
hw/i386/pc_piix.c | 16 ++-
hw/i386/pc_q35.c | 9 +-
system/bootdevice.c | 25 +++--
hw/core/meson.build | 1 +
15 files changed, 587 insertions(+), 120 deletions(-)
create mode 100644 include/hw/core/resetcontainer.h
create mode 100644 hw/core/resetcontainer.c