Re: [PATCH 2/4] sysctl/libxl: Add interface for returning IO topology data

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 12/05/2014 11:03 AM, Jan Beulich wrote:
>>>> On 05.12.14 at 16:55, <JBeulich@suse.com> wrote:
>>>>> On 02.12.14 at 22:34, <boris.ostrovsky@oracle.com> wrote:
>>> +struct xen_sysctl_iotopo {
>>> +    uint16_t seg;
>>> +    uint8_t bus;
>>> +    uint8_t devfn;
>>> +    uint32_t node;
>>> +};
>> This is PCI-centric without expressing in the name or layout.

xen_sysctl_pcitopo would be a better name.

>>   Perhaps
>> the first part should be a union from the very beginning?
> And I wonder whether that supposed union part wouldn't be nicely
> done using struct physdev_pci_device.

The do look strikingly similar ;-)

How would a union be useful here?

>
> Additionally please add IN and OUT annotations. When I first saw
> this I assumed they would all be OUT (in which case the long running
> loop problem mentioned in the reply to one of the other patches
> wouldn't have been there), matching their CPU counterpart...

I don't follow this. Are you saying that if ti->max_devs in patch 3/4 is 
an IN (which it is) then we don't have to guard for long-running loops?

-boris