Re: [Qemu-devel] [PATCH v12 00/15] vfio-pci: pass the aer error to guest

[Chen, Hanxiao]

Hi, Alex

> -----Original Message-----
> From: Alex Williamson [mailto:address@hidden
> To: Chen, Hanxiao
> Cc: address@hidden; Chen, Fan
> Subject: Re: [Qemu-devel] [PATCH v12 00/15] vfio-pci: pass the aer error to 
> guest
> 
> On Thu, 2015-07-16 at 12:00 +0800, Chen Hanxiao wrote:
> > From: Chen Fan <address@hidden>
> >
> > For now, when qemu receives an error from host aer report
> > by vfio pci passthough devices, qemu just terminate the guest.
> > Usually user want to know what error occurred
> > rather than stop the guest.
> >
> > This patches add aer capability support for vfio device,
> > then pass the error to guest, and let guest driver to recover
> > from the error.
> > Turning on SERR# for error forwording in bridge control register
> > patch in seabios has been merged as commit 32ec3ee.
> >
> > notes:
> >   this series patches enable aer support single/multi-function,
> >   for multi-function, require all the function of the slot assigned to
> >   VM and on the same slot.
> >
> > Chen Fan (15):
> >   vfio: extract vfio_get_hot_reset_info as a single function
> >   vfio: squeeze out vfio_pci_do_hot_reset for support bus reset
> >   pcie: modify the capability size assert
> >   vfio: make the 4 bytes aligned for capability size
> >   vfio: add pcie extanded capability support
> >   aer: impove pcie_aer_init to support vfio device
> >   vfio: add aer support for vfio device
> >   vfio: add check host bus reset is support or not
> >   pci: add bus reset_notifiers callbacks for host bus reset
> >   vfio: add sec_bus_reset notifier to notify physical bus reset is
> >     needed
> >   vfio: modify vfio_pci_hot_reset to support bus reset
> >   vfio: do hot bus reset when do virtual secondary bus reset
> >   pcie_aer: expose pcie_aer_msg() interface
> >   vfio-pci: pass the aer error to guest
> >   vfio: add 'aer' property to expose aercap
> >
> >  hw/pci-bridge/ioh3420.c            |   2 +-
> >  hw/pci-bridge/xio3130_downstream.c |   2 +-
> >  hw/pci-bridge/xio3130_upstream.c   |   2 +-
> >  hw/pci/pci.c                       |  16 +
> >  hw/pci/pci_bridge.c                |   6 +
> >  hw/pci/pcie.c                      |   2 +-
> >  hw/pci/pcie_aer.c                  |   6 +-
> >  hw/vfio/pci.c                      | 636 
> > +++++++++++++++++++++++++++++++++----
> >  include/hw/pci/pci.h               |   4 +
> >  include/hw/pci/pci_bus.h           |   2 +
> >  include/hw/pci/pcie_aer.h          |   3 +-
> >  11 files changed, 609 insertions(+), 72 deletions(-)
> 
> 
> This seems to be pretty much the same as v11 where I commented that I
> didn't think it was acceptable to have a feature dependent on having all
> the functions assigned without supporting hot-add of multi-function
> devices.  Can you summarize what's changed here and whether that comment
> was addressed.  It would be a courtesy to reviewers to provide at least
> a summary changelog with each new version.  Thanks,
> 

We could hot-unplug all passthrough devices by device_del,
But currently Qemu could not hot-add multi-function pci device.

See TODO in pcie_cap_slot_hotplug_cb:
/* TODO: multifunction hot-plug.
 * Right now, only a device of function = 0 is allowed to be
 * hot plugged/unplugged.
 */
assert(PCI_FUNC(pci_dev->devfn) == 0);

So we had to limit this as a workaround.

Why can't  we add functions one by one to the same slot by device_add?

If we could add functions one by one,
then we can enable aer for the devices once all dependence functions
were added by setting aer as a dynamic property(such as using 
object_property_add, qom-set)

How do you think?

Regards,
- Chen