Re: [PATCH RFC RESEND v2 3/6] hw/pci: Add pci_root_bus_max_bus

[Xingang Wang]

Hi Eric,

On 2021/4/13 16:05, Auger Eric wrote:
> Hi Xingang,
>
> On 3/25/21 8:22 AM, Wang Xingang wrote:
> > From: Xingang Wang <wangxingang5@huawei.com>
> >
> > This helps to find max bus number of a root bus.
> s/max bus number of a root bus/highest bus number of a bridge hierarchy?

Thanks, I will change the description.

> > Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
> > Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
> > ---
> >   hw/pci/pci.c         | 34 ++++++++++++++++++++++++++++++++++
> >   include/hw/pci/pci.h |  1 +
> >   2 files changed, 35 insertions(+)
> >
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index e17aa9075f..c7957cbf7c 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -538,6 +538,40 @@ int pci_bus_num(PCIBus *s)
> >       return PCI_BUS_GET_CLASS(s)->bus_num(s);
> >   }
> >   
> > +int pci_root_bus_max_bus(PCIBus *bus)
> > +{
> > +    PCIHostState *host;
> > +    PCIDevice *dev;
> > +    int max_bus = 0;
> > +    int type, devfn;
> > +    uint8_t subordinate;
> > +
> > +    if (!pci_bus_is_root(bus)) {
> > +        return 0;
> > +    }
> > +
> > +    host = PCI_HOST_BRIDGE(BUS(bus)->parent);
> > +    max_bus = pci_bus_num(host->bus);
> > +
> > +    for (devfn = 0; devfn < ARRAY_SIZE(host->bus->devices); devfn++) {
> > +        dev = host->bus->devices[devfn];
> > +
> > +        if (!dev) {
> > +            continue;
> > +        }
> > +
> > +        type = dev->config[PCI_HEADER_TYPE] & ~PCI_HEADER_TYPE_MULTI_FUNCTION;
> Seems there is PCI_DEVICE_GET_CLASS(dev)->is_bridge (see
> pci_root_bus_in_range). Can't that be used instead?

Thanks, I will simplify this.

> > +        if (type == PCI_HEADER_TYPE_BRIDGE) {
> > +            subordinate = dev->config[PCI_SUBORDINATE_BUS];
> > +            if (subordinate > max_bus) {
> > +                max_bus = subordinate;
> what about the secondary bus number, it is always less than the others?

Thanks, the secondary bus number should be taken into account. Maybe a 
pci_root_bus_range to get [min_bus, max_bus] would be better.

> Thanks
>
> Eric
> > +            }
> > +        }
> > +    }
> > +
> > +    return max_bus;
> > +}
> > +
> >   int pci_bus_numa_node(PCIBus *bus)
> >   {
> >       return PCI_BUS_GET_CLASS(bus)->numa_node(bus);
> > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > index 718b5a454a..e0c69534f4 100644
> > --- a/include/hw/pci/pci.h
> > +++ b/include/hw/pci/pci.h
> > @@ -450,6 +450,7 @@ static inline PCIBus *pci_get_bus(const PCIDevice *dev)
> >       return PCI_BUS(qdev_get_parent_bus(DEVICE(dev)));
> >   }
> >   int pci_bus_num(PCIBus *s);
> > +int pci_root_bus_max_bus(PCIBus *bus);
> >   static inline int pci_dev_bus_num(const PCIDevice *dev)
> >   {
> >       return pci_bus_num(pci_get_bus(dev));
>
> .

Xingang

.