[libvirt] [PATCH v2 2/4] qemu: Use generic PCIe Root Ports by default when available

[Laine Stump]

On 03/17/2017 05:06 AM, Andrea Bolognani wrote:
> On Thu, 2017-03-16 at 18:30 -0400, Laine Stump wrote:
>>> @@ -1861,7 +1863,12 @@ qemuDomainPCIControllerSetDefaultModelName(virDomainControllerDefPtr cont)
>>>           *modelName = VIR_DOMAIN_CONTROLLER_PCI_MODEL_NAME_I82801B11_BRIDGE;
>>>           break;
>>>       case VIR_DOMAIN_CONTROLLER_MODEL_PCIE_ROOT_PORT:
>>> -        *modelName = VIR_DOMAIN_CONTROLLER_PCI_MODEL_NAME_IOH3420;
>>> +        /* Use generic PCIe Root Ports if available, falling back to
>>> +         * ioh3420 otherwise */
>>> +        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_PCIE_ROOT_PORT))
>>> +            *modelName = VIR_DOMAIN_CONTROLLER_PCI_MODEL_NAME_PCIE_ROOT_PORT;
>>> +        else
>>> +            *modelName = VIR_DOMAIN_CONTROLLER_PCI_MODEL_NAME_IOH3420;
>>  
>> I wonder if we should check caps for IOH3420 here just to be consistent
>> (and log an error if neither is available). I realize that's not the way
>> it worked before (existing code only checks the caps for a particular
>> device at the time we generate the commandline), but I'll be the first
>> to admit my original code was, err, "less than ideal".
>>  
>> It's up to you though, add it or not.
> 
> We already check when building the QEMU command line, which
> is the appropriate place IMHO. I'd rather not duplicate the
> check here as well.

It all depends on whether you want to get an error when you define the
domain, or not until you try to start it. I prefer the latter, but in
this case it's all just academic, since we know that all qemu binaries
we recognize as having a PCIe root bus also support the ioh3420.