Re: [PATCH v2 5/5] hw/pci: ensure PCIE devices are plugged into only slot 0 of PCIE port

[Ani Sinha]

> On 26-Jun-2023, at 2:41 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> 
> On Fri, Jun 23, 2023 at 04:57:20PM +0200, Julia Suvorova wrote:
>> On Thu, Jun 22, 2023 at 7:48 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>>> 
>>> On Thu, Jun 22, 2023 at 05:46:40PM +0200, Julia Suvorova wrote:
>>>> On Thu, Jun 22, 2023 at 12:34 PM Ani Sinha <anisinha@redhat.com> 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.
>>>>> 
>>>>> CC: jusual@redhat.com
>>>>> CC: imammedo@redhat.com
>>>>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2128929
>>>>> Signed-off-by: Ani Sinha <anisinha@redhat.com>
>>>>> ---
>>>>> hw/pci/pci.c | 6 ++++++
>>>>> 1 file changed, 6 insertions(+)
>>>>> 
>>>>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>>>>> index bf38905b7d..5f25ab9f5e 100644
>>>>> --- a/hw/pci/pci.c
>>>>> +++ b/hw/pci/pci.c
>>>>> @@ -64,6 +64,7 @@ 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),
>>>>> @@ -1189,6 +1190,11 @@ static PCIDevice *do_pci_register_device(PCIDevice 
>>>>> *pci_dev,
>>>>>                    name);
>>>>> 
>>>>>        return NULL;
>>>>> +    } else if (pcie_has_upstream_port(pci_dev) && PCI_SLOT(devfn)) {
>>>>> +        error_setg(errp, "PCI: slot %d is not valid for %s,"
>>>>> +                   " PCI express devices can only be plugged into slot 
>>>>> 0.",
>>>> 
>>>> This is not technically correct, because downstream ports and root
>>>> ports are also PCIe devices, and they can have different slots under
>>>> upstream ports and RC. But this error will never be shown for them, so
>>>> it seems fine.
>>> 
>>> Hmm. Confusing users is not nice ... I agree this might
>>> make people think they can not use root ports in slot !=0 either.
>>> 
>>> Would you add "with an upstream port"?
>>> E.g. "PCI Express devices with an upstream port" ?
>> 
>> This whole upstream port conditioning is quite confusing.
>> How about "%parent device% only allows plugging into slot 0"?
>> 
>> Best regards, Julia Suvorova.
> 
> Good idea!

OK I will send out another iteration once Igor has a chance to take a look at 
the test fixes or someone else reviews them. 

> 
>>>> 
>>>> Reviewed-by: Julia Suvorova <jusual@redhat.com>
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> +                   PCI_SLOT(devfn), name);
>>>>> +        return NULL;
>>>>>     }
>>>>> 
>>>>>     pci_dev->devfn = devfn;
>>>>> --
>>>>> 2.39.1
>>>>> 
>>> 
>