linux-kernel - Re: Use CPUID to communicate with the hypervisor.

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Date:	Fri, 26 Sep 2008 17:32:26 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	akataria@...are.com
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"avi@...hat.com" <avi@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Zach Amsden <zach@...are.com>,
	Daniel Hecht <dhecht@...are.com>,
	"Jun.Nakajima@...el.Com" <Jun.Nakajima@...el.Com>
Subject: Re: Use CPUID to communicate with the hypervisor.

Alok Kataria wrote:
>>>
>> This is great, obviously... although we'll have to deal with legacy
>> methods for a while if not indefinitely (just as we have to for
>> pre-CPUID processors).
> 
> Ok, do you think we should keep those (legacy) interfaces separate so
> that they can be phased out whenever the time is right. 
> 

I don't, realistically, think we can phase them out for a very long 
time, and then it's usually a "why bother".  What we want to do is 
abstract them so they don't make the rest of the code suck.

> 
> I would like to see this as a generic hypervisor way to get frequency
> rather than a VMware specific thingy. 
>> In order for *that* to be safe, you'd have to have well-defined ranges
>> for different virtualization vendors where each of them can define their
>> own stuff.
> 
> My motivation for doing this is to have a standard across all the
> hypervisor's. If all the different hypervisor guys can come to some
> sought of consensus on the various hypervisor leafs that would help keep
> this simple and a lot more maintainable.
> 

Agreed.  However, that's obviously beyond our immediate control.

	-hpa
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