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 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.

> 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