One question come to my mind for "but such changes will only be additive", which may be an issue in cloud environment: Considering following assumed situation: In release 1.0's cpu_maps.xml, core2duo include feature "a, b, c" In release 1.1's cpu_maps.xml, core2duo include "a, b, c, d" Two hosts, with different CPU features: Host A with feature "a, b, c, d, e" and 1.1 release, capabilities will be: Model: Core2duo (assume core2duo is the only match one) Features: e Host B with feature "a, b, c, e", and 1.0 release, capabilities will be: Models: Core2Duo (again, assume core2duo is the only match one) Features: e When we compare the capabilities in Host A, I think comparCPU will pass, because host A will use 1.1 release definition to check Host B's capabilities, this is sure to be wrong, since host B does not have feature 'd'. I think the key point is, capabilities describe features with information from cpu_maps.xml, which is a per-host file. Thanks --jyh Will depends on
-----Original Message----- From: Jiang, Yunhong Sent: Friday, November 02, 2012 9:39 AM To: Eric Blake Cc: libvir-list@redhat.com Subject: RE: [libvirt] Is possible that cpu_maps.xml changed during different releases?
Eric, thanks for the answer very .much, that's really helpful. Sorry for the wrong format, I'm using outlook and possibly some setting wrong.
Thanks --jyh
-----Original Message----- From: Eric Blake [mailto:eblake@redhat.com] Sent: Thursday, November 01, 2012 11:23 PM To: Jiang, Yunhong Cc: libvir-list@redhat.com Subject: Re: [libvirt] Is possible that cpu_maps.xml changed during different releases?
On 10/31/2012 02:20 AM, Jiang, Yunhong wrote:
Hi, all
[your mailer doesn't know how to wrap long lines, which makes it awkward to read your message]
I have two questions to the cpu_maps.xml in different releases, hope someone can give me some hints:
a) Will it be possible that the features defined in cpu_maps.xml for one specific CPU model (like Nehalem) will be different? For example, one feature is not listed for Nehalem in release x.y, and added in release x.y+1?
XML does have the possibility to change between releases, but such changes will only be additive (we will never remove support for a feature once it is listed).
2) Is the format of the cpu_maps.xml fine defined or will be it changed
during releases? I asked this because currently the features defined in the capabilities only list features not included in the definition in cpu_maps.xml for the corresponding model. So if I want to get the full features supported by the host, I have to parse the capabilities and the cpu_maps.xml. I didn't find the definition for cpu_maps.xml format, although the capabilities format is well defined in http://libvirt.org/guide/html/Application_Development_Guide-Connection s-Ca pability_Info.html.
The format should be well-defined; again, our requirement is that upgrades might add new xml attributes or elements, but will never remove elements that have been valid in previous releases. To some extent, docs/schemas/capability.rng in libvirt.git gives an RNG grammar for what capabilities will look like, although someone else may be able to point to a better documentation of what will be in cpu_maps.xml.
-- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org