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

[Chen Fan]

On 03/27/2016 08:19 PM, Michael S. Tsirkin wrote:
> On Thu, Mar 24, 2016 at 04:54:33PM -0600, Alex Williamson wrote:
> > On Wed, 23 Mar 2016 18:12:02 +0800
> > Cao jin <address@hidden> wrote:
> >
> > > From: Chen Fan <address@hidden>
> > >
> > > 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 <address@hidden>
> > > ---
> > >   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.
for non-hotplug case, we used machine_done_notifier to check
the bus reset functionality. because we can't ensure the function 0
was initialized at last when cold boot up.
> Also, why does it scan all devices on bus, not all functions
> of the device?
I can fix this by testing the bridge whether support ARI.

Thanks.
Chen

> > > 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;
>
> .