RE: [Xen-users] Running Xen on current Opteron family?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

To run unmodified guests, you do need SVM (AMD Virtualization Technology, formely codenamed Pacifiica). Nothing else will work. And by the way, don't expect a 3-5% overhead when running unmodified OS's, it's just not possible with that type of architecture, without further additions, such as para-virtualized drivers. This obviously will depend on the amount of hardware accesses that happen in the system, but it's most likely going to be a fair bit higher. The 3-5% figure is based on para-virtulized guests, so guests that have modified source-code. It would be possible to get pretty close to that by having para-virtualized drivers, so that hardware accesses are not done by intercepting the actual hardware access and translatiing each individual hardware access into a packet of data-request for the service OS and then transferring the result back to the guest with another set of intercepts - each intercept is quite time-consuming, and a driver that had a more direct interface (rather than using a "hardware" interface, we'd use a "software" interface, so the information is more conveniently packaged for the service-OS, and there's much less need to work out what's going on from multiple hardware accesses).

 

The current generation of Opteron processors does support Para-virtualized Xen. There will be new models of Opteron processors with SVM available later this year - I'm not sure exactly when, as I'm not part of the team that launches new processors [and of course, even _IF_ I did know, I would not be allowed to say, as release dates are supposed to be secret...]

 

--

Mats

 

 

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From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Sanket Agrawal
Sent: 24 May 2006 16:36
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Running Xen on current Opteron family?

I have been looking at XenSource 3.0 solution for running virtual servers on opteron servers. According to XenSource's documentation, it runs on Opterons with pacifica feature. My understanding is that we need this feature for following reaons:

- lower virtualization overhead. Theoretically, 3-5% overhead for guest oses when virtualized
- running guest OSes without source code - useful for running Windows 2003 in addition to linux and solaris for testing

However, the pacifica feature is not present in current opteron family. After googling, I found out that it has been renamed to "Secure Virtual Machine Extension" for opterons and is scheduled for release for upcoming Athlon processor releases with socket 'F'. I checked with HP and they confirmed that pacifica feature is planned to be released with socket 'F' in opterons. There is no firm release date yet, to the best of my knowledge.

Given that pacifica feature is not implemented in Opterons (unless "Direct Connection Architecture" qualifies as a pacifica feature?), my question is whether XenSource 3.0 can still be run on current opteron 2xx families with low overhead and without source code for guest OSes, as documented in the "info" section of XenSource 3.0.

Thanks,
Sanket

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