Re: [Qemu-devel] [patch v5 07/12] pci: add a pci_function_is_valid callback to check function if valid

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Mar 24, 2016 at 04:54:33PM -0600, Alex Williamson wrote:
> On Wed, 23 Mar 2016 18:12:02 +0800
> Cao jin <caoj.fnst@cn.fujitsu.com> wrote:
> 
> > From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> > 
> > PCI hotplug requires that function 0 is added last to close the
> > slot.  Since vfio supporting AER, we require that the VM bus
> > contains the same set of devices as the host bus to support AER,
> > we can perform an AER validation test whenever a function 0 in
> > the VM is hot-added.
> > 
> > Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> > ---
> >  hw/pci/pci.c         | 32 ++++++++++++++++++++++++++++++++
> >  include/hw/pci/pci.h |  1 +
> >  2 files changed, 33 insertions(+)
> 
> 
> This would of course need Michael's ack.
> 
> Michael, we can't do this in vfio-pci code because we can't guarantee
> that function 0 is a vfio-pci device.  That would allow users to bypass
> our configuration requirements by putting any random non-vfio-pci
> device at function 0 of a hot-added multifunction device.

I got that. What I don't understand is how is the non hotplug
variant handled, given that is_valid_func is not called
in that case.

Also, why does it scan all devices on bus, not all functions
of the device?

> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index e67664d..2a5291a 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -1840,6 +1840,22 @@ PCIDevice *pci_find_device(PCIBus *bus, int bus_num, uint8_t devfn)
> >      return bus->devices[devfn];
> >  }
> >  
> > +static void pci_function_is_valid(PCIBus *bus, PCIDevice *d, void *opaque)
> > +{
> > +    PCIDeviceClass *pc = PCI_DEVICE_GET_CLASS(d);
> > +    Error **errp = opaque;
> > +
> > +    if (*errp) {
> > +        return;
> > +    }
> > +
> > +    if (!pc->is_valid_func) {
> > +        return;
> > +    }
> > +
> > +    pc->is_valid_func(d, errp);
> > +}
> > +
> >  static void pci_qdev_realize(DeviceState *qdev, Error **errp)
> >  {
> >      PCIDevice *pci_dev = (PCIDevice *)qdev;
> > @@ -1882,6 +1898,22 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
> >          pci_qdev_unrealize(DEVICE(pci_dev), NULL);
> >          return;
> >      }
> > +
> > +    /*
> > +     *  If the function number is 0, indicate the closure of the slot.
> > +     *  then we get the chance to check all functions on same device
> > +     *  if valid.
> > +     */
> > +    if (DEVICE(pci_dev)->hotplugged &&
> > +        pci_get_function_0(pci_dev) == pci_dev) {
> > +        pci_for_each_device(bus, pci_bus_num(bus),
> > +                            pci_function_is_valid, &local_err);
> > +        if (local_err) {
> > +            error_propagate(errp, local_err);
> > +            pci_qdev_unrealize(DEVICE(pci_dev), NULL);
> > +            return;
> > +        }
> > +    }
> >  }
> >  
> >  static void pci_default_realize(PCIDevice *dev, Error **errp)
> > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > index 0be07c8..4a2f7d4 100644
> > --- a/include/hw/pci/pci.h
> > +++ b/include/hw/pci/pci.h
> > @@ -190,6 +190,7 @@ typedef struct PCIDeviceClass {
> >  
> >      void (*realize)(PCIDevice *dev, Error **errp);
> >      int (*init)(PCIDevice *dev);/* TODO convert to realize() and remove */
> > +    void (*is_valid_func)(PCIDevice *dev, Error **errp);
> >      PCIUnregisterFunc *exit;
> >      PCIConfigReadFunc *config_read;
> >      PCIConfigWriteFunc *config_write;