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

[Michael S. Tsirkin]

On Thu, Oct 03, 2013 at 05:58:30PM +0200, Paolo Bonzini wrote:
> 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

x86 kvm only?

> >> 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(-)
> > 
> >