Re: [Qemu-devel] [RFC PATCH v2 4/4] pci: enable RedHat PCI bridges to reserve additional buses on PCI init

[Alexander Bezzubikov]

2017-07-23 5:49 GMT+03:00 Michael S. Tsirkin <address@hidden>:

> On Sun, Jul 23, 2017 at 01:11:50AM +0300, Aleksandr Bezzubikov wrote:
> > In case of Red Hat PCI bridges reserve additional buses, which number is
> provided
> > in a vendor-specific capability.
> >
> > Signed-off-by: Aleksandr Bezzubikov <address@hidden>
> > ---
> >  src/fw/pciinit.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> > index 864954f..f05a8b9 100644
> > --- a/src/fw/pciinit.c
> > +++ b/src/fw/pciinit.c
> > @@ -15,6 +15,7 @@
> >  #include "hw/pcidevice.h" // pci_probe_devices
> >  #include "hw/pci_ids.h" // PCI_VENDOR_ID_INTEL
> >  #include "hw/pci_regs.h" // PCI_COMMAND
> > +#include "hw/pci_cap.h" // qemu_pci_cap
> >  #include "list.h" // struct hlist_node
> >  #include "malloc.h" // free
> >  #include "output.h" // dprintf
> > @@ -578,9 +579,18 @@ pci_bios_init_bus_rec(int bus, u8 *pci_bus)
> >          pci_bios_init_bus_rec(secbus, pci_bus);
> >
> >          if (subbus != *pci_bus) {
> > +            u8 res_bus = 0;
> > +            if (pci_config_readw(bdf, PCI_VENDOR_ID) ==
> PCI_VENDOR_ID_REDHAT) {
>
> Check device ID as well.

Not sure what ID/IDs we want to see here exactly. Now it can be
only pcie-root-port (0xC then), but


>
> > +                u8 cap = pci_find_capability(bdf, PCI_CAP_ID_VNDR, 0);
>
> There could be multiple vendor capabilities. You want to scan them all.
>
>
> > +                if (cap) {
> > +                    res_bus = pci_config_readb(bdf,
> > +                            cap + offsetof(struct redhat_pci_bridge_cap,
> > +                                           bus_res));
>
>
> You might want to add sanity checks e.g. overflow, and capability
> length.
>
> Also, if all you use is offsetof, don't bother with a struct, just
> add some defines.
>
OK, will move this to defines.


>
> > +                }
> > +            }
> >              dprintf(1, "PCI: subordinate bus = 0x%x -> 0x%x\n",
> > -                    subbus, *pci_bus);
> > -            subbus = *pci_bus;
> > +                    subbus, *pci_bus + res_bus);
> > +            subbus = *pci_bus + res_bus;
>
> So you take all present devices and add reserved ones - is that it?
> If so it looks like this will steal extra buses each time you
> add a child bus and reboot.
>

You're right, such problem persists. Will think on what can be done here.


>
>
> >          } else {
> >              dprintf(1, "PCI: subordinate bus = 0x%x\n", subbus);
> >          }
> > --
> > 2.7.4
>



-- 
Alexander Bezzubikov