[libvirt] [PATCH v2 1/2] Add pcihole64 attribute to root PCI controllers

Ján Tomko jtomko at redhat.com
Tue Aug 13 10:24:51 UTC 2013

On 08/13/2013 11:54 AM, Daniel P. Berrange wrote:
> On Tue, Aug 13, 2013 at 11:53:42AM +0200, Ján Tomko wrote:
>> On 08/13/2013 10:55 AM, Daniel P. Berrange wrote:
>>> On Tue, Aug 13, 2013 at 10:51:04AM +0200, Ján Tomko wrote:
>>>> <controller type='pci' index='0' model='pci-root' pcihole64='1'/>
>>>> It can be used to adjust (or disable) the size of the 64-bit
>>>> PCI hole. The size attribute is in gigabytes, since it would
>>>> get rounded up to nearest GB by QEMU anyway.
>>> Choosing the units based on what one specific hypervisor happens to
>>> currently do has proven to be a pretty bad idea in the past. I'd say
>>> we should be using KB here. Or better yet, have this as a separate
>>> child element, and then support a 'units' attribute at the same time,
>>> defaulting to KB. 
>> Would it be okay to use the largest usable unit when formatting the XML
>> to make it more human-friendly?
> No, because you'd be throwing away data if the user had requested less
> than a GB. Outputting XML should use the smallest unit for which we
> want to support, which IMHO should be KB.

By 'usable' I meant the unit that is the largest divisor of the size, e.g.:
512 KB would stay 512 KB, but 2048 MB would get translated to 2 GB.

But this requires the applications parsing the XML to read both the size and
the units.


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