From: Andi Kleen <ak@suse.de>
To: Chris Wright <chrisw@sous-sol.org>
Subject: Re: [RFC, PATCH 1/24] i386 Vmi documentation
Date: Wed, 22 Mar 2006 22:13:43 +0100
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Cc: virtualization@lists.osdl.org, Zachary Amsden <zach@vmware.com>,
       Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Xen-devel <xen-devel@lists.xensource.com>,
       Andrew Morton <akpm@osdl.org>, Dan Hecht <dhecht@vmware.com>,
       Dan Arai <arai@vmware.com>, Anne Holler <anne@vmware.com>,
       Pratap Subrahmanyam <pratap@vmware.com>,
       Christopher Li <chrisl@vmware.com>, Joshua LeVasseur <jtl@ira.uka.de>,
       Chris Wright <chrisw@osdl.org>, Rik Van Riel <riel@redhat.com>,
       Jyothy Reddy <jreddy@vmware.com>, Jack Lo <jlo@vmware.com>,
       Kip Macy <kmacy@fsmware.com>, Jan Beulich <jbeulich@novell.com>,
       Ky Srinivasan <ksrinivasan@novell.com>,
       Wim Coekaerts <wim.coekaerts@oracle.com>,
       Leendert van Doorn <leendert@watson.ibm.com>
References: <200603131759.k2DHxeep005627@zach-dev.vmware.com> <200603222105.58912.ak@suse.de> <20060322213435.GI15997@sorel.sous-sol.org>
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On Wednesday 22 March 2006 22:34, Chris Wright wrote:
> * Andi Kleen (ak@suse.de) wrote:
> > On Monday 13 March 2006 18:59, Zachary Amsden wrote:
> > 
> > > +     The general mechanism for providing customized features and
> > > +     capabilities is to provide notification of these feature through
> > > +     the CPUID call, 
> > 
> > How should that work since CPUID cannot be intercepted by 
> > a Hypervisor (without VMX/SVM)?  
> 
> Yeah, it requires guest kernel cooperation/modification.

Even then it's useless for many flags because any user program can (and will) 
call CPUID directly. 
 
> > > +   The net result of these choices is that most of the calls are very
> > > +   easy to make from C-code, and calls that are likely to be required in
> > > +   low level trap handling code are easy to call from assembler.   Most
> > > +   of these calls are also very easily implemented by the hypervisor
> > > +   vendor in C code, and only the performance critical calls from
> > > +   assembler paths require custom assembly implementations.
> > > +
> > > +   CORE INTERFACE CALLS
> > 
> > Did I miss it or do you never describe how to find these entry points? 
> 
> It's the ROM interface.  For native they are emitted directly inline.
> For non-native, they are emitted as call stubs, which call to the ROM.
> I don't recall if it's in this doc, but the inline patch has all the
> gory details.

Sure the point was if they write this long fancy document why stop
at documenting the last 5%?

-Andi
 
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