Re: [PATCH v6 5/5] hw/pci: ensure PCIE devices are plugged into only slot 0 of PCIE port

[Michael S. Tsirkin]

On Thu, Jun 29, 2023 at 08:07:57PM +0530, Ani Sinha wrote:
> 
> 
> > On 29-Jun-2023, at 7:54 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > 
> > On Thu, Jun 29, 2023 at 09:37:07AM +0530, Ani Sinha wrote:
> >> PCI Express ports only have one slot, so PCI Express devices can only be
> >> plugged into slot 0 on a PCIE port. Enforce it.
> >> 
> >> The change has been tested to not break ARI by instantiating seven vfs on 
> >> an
> >> emulated igb device (the maximum number of vfs the linux igb driver 
> >> supports).
> > 
> > I guess we need to test with some other device then? 7 VFs is same
> > slot so hardly a good test.
> 
> No its not the same slot. Its using different slots/device numbers. I checked 
> that.
> The same patch was failing without the vf check.

Ah, playing with VF stride? Could you show the command line please?

> > 
> >> The vfs are seen to have non-zero device/slot numbers in the conventional
> >> PCI BDF representation.
> >> 
> >> CC: jusual@redhat.com
> >> CC: imammedo@redhat.com
> >> CC: akihiko.odaki@daynix.com
> >> 
> >> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2128929
> >> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> >> Reviewed-by: Julia Suvorova <jusual@redhat.com>
> >> ---
> >> hw/pci/pci.c | 15 +++++++++++++++
> >> 1 file changed, 15 insertions(+)
> >> 
> >> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> >> index e2eb4c3b4a..0320ac2bb3 100644
> >> --- a/hw/pci/pci.c
> >> +++ b/hw/pci/pci.c
> >> @@ -65,6 +65,7 @@ bool pci_available = true;
> >> static char *pcibus_get_dev_path(DeviceState *dev);
> >> static char *pcibus_get_fw_dev_path(DeviceState *dev);
> >> static void pcibus_reset(BusState *qbus);
> >> +static bool pcie_has_upstream_port(PCIDevice *dev);
> >> 
> >> static Property pci_props[] = {
> >>     DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
> >> @@ -1190,6 +1191,20 @@ static PCIDevice *do_pci_register_device(PCIDevice 
> >> *pci_dev,
> >>                    name);
> >> 
> >>        return NULL;
> >> +    } /*
> >> +       * With SRIOV and ARI, vfs can have non-zero slot in the 
> >> conventional
> >> +       * PCI interpretation as all five bits reserved for slot addresses 
> >> are
> >> +       * also used for function bits for the various vfs. Ignore that 
> >> case.
> >> +       * It is too early here to check for ARI capabilities in the PCI 
> >> config
> >> +       * space. Hence, we check for a vf device instead.
> >> +       */
> >> +    else if (!pci_is_vf(pci_dev) &&
> >> +             pcie_has_upstream_port(pci_dev) &&
> >> +             PCI_SLOT(devfn)) {
> >> +        error_setg(errp, "PCI: slot %d is not valid for %s,"
> >> +                   " parent device only allows plugging into slot 0.",
> >> +                   PCI_SLOT(devfn), name);
> >> +        return NULL;
> >>     }
> >> 
> >>     pci_dev->devfn = devfn;
> >> -- 
> >> 2.39.1
> >