Re: [Qemu-devel] [PATCH 0/4] qdev: switch reset to post-order, clean up PCI reset

[Paolo Bonzini <pbonzini@redhat.com>]

Il 03/10/2013 15:54, Michael S. Tsirkin ha scritto:
> On Thu, Oct 03, 2013 at 03:46:11PM +0200, Paolo Bonzini wrote:
>> PCI is handling resetting of its devices before the bus is reset,
>> but this is only necessary because qdev is broken and usually does
>> pre-order reset.  Post-order is a much better definition.  Drop
>> the unnecessary flexibility that lets bus decide the reset order,
>> convert to post-order, and make PCI use common code for reset.
> 
> Need to go carefully here. I remember a bunch of targets
> were relying on reset in this order, though don't
> have the detail right now.

The main change is that sub-devices, which basically exist only for USB,
virtio, and SCSI, are reset _before_ the corresponding parent device
(the USB host controller, virtio proxy device, or SCSI HBA).

For SCSI, this patch fixes bugs that I'm currently working around in
virtio-scsi (see the manual reset in virtio_scsi_reset, that manually
resets the subdevices).

USB and virtio are not using qdev reset at all, so they are unaffected
by the patches.  They rely on the parent device's own reset method to
propagate the reset.  virtio already uses post-order, so it could be
changed to use qdev reset, but I don't plan to do it unless it fixes
bugs.  USB is more complicated and I don't really understand it.

For PCI, the change is that all devices are reset first, and then the
interrupts state and config space are reset for all devices.

> What kind of testing did this patchset go through?

For each PCI device I tried creating a VM with an instance of it (a few
devices at a time), and did VM resets.  Earlier versions were tested by
the guy who reported the SCSI problems.

Paolo

>> Paolo Bonzini (4):
>>   pci: do not export pci_bus_reset
>>   pci: clean up resetting of IRQs
>>   qdev: allow both pre- and post-order vists in qdev walking functions
>>   qdev: switch reset to post-order
>>
>>  hw/core/qdev.c         |   47 ++++++++++++++++++++++++++++++++++-------------
>>  hw/pci/pci.c           |   42 ++++++++++++++++++++----------------------
>>  hw/pci/pci_bridge.c    |    2 +-
>>  include/hw/pci/pci.h   |    1 -
>>  include/hw/qdev-core.h |   15 ++++++++++-----
>>  5 files changed, 65 insertions(+), 42 deletions(-)
> 
>