Re: [Xen-devel] [PATCH for-4.5 v6 05/16] tools: Add vmware_port support

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 09/25/2014 12:24 PM, Ian Campbell wrote:
> On Wed, 2014-09-24 at 12:31 -0400, Don Slutz wrote:
> > On 09/23/14 08:20, Ian Campbell wrote:
> > > On Mon, 2014-09-22 at 12:42 -0400, Don Slutz wrote:
> > > > > The latter would allow moving to buildinfo.u.hvm, which would be nicer
> > > > > from the libxl PoV, I think.
> > > > I could not find "buildinfo.u.hvm":
> > > >
> > > >
> > > > dcs-xen-54:~/xen>git grep buildinfo.u.hvm
> > > > dcs-xen-54:~/xen>
> > > >
> > > >
> > > > So unable to comment.
> > > It's in the idl, next to createinfo.
> > I take that to mean:
> >
> >
> > libxl_domain_config = Struct("domain_config", [
> >       ("c_info", libxl_domain_create_info),
> >       ("b_info", libxl_domain_build_info),
> > ...
> >
> > I.E.
> >
> > b_info->u.hvm
> Yes.
>
>
> > > >     Currently I do not know of a way to
> > > > say "set vmware_hw to 7
> > > > if vmware_port is true and vmware_hw is not specified".
> > > That's an error case, isn't it? Or at least a vmware_port is ignored
> > > case.
> > Nope.  But I will agree that I have not done a lot with 3 (at least)
> > state booleans.  The 3 states being true, false, and not specified.
> The third state is "default" as in: libxl sets something sensible based
> on other criteria (internal choice, other settings etc).
>
> > And vmware_port is not ignored.
> >
> > > What I suggested was "if vmware_hw is non-zero then set vmware_port".
> > I am reading that as "set vmware_port if not specified".  To avoid
> > complexity, I am treating vmware_hw as a boolean.  Using this
> > I get the following table:
> >
> > _hw   _port
> >    0     0        Just like today
> >    1     0        Only cpuid leaves change -- very unlikey
> >    1     1        Full VMware mode
> >    0     1        VMware hyper call mode.
> >
> > Adding U for unspecified:
> >
> > _hw   _port
> >    U     U        ==> _hw=0 _port=0
> >    0     U        ==> _hw=0 _port=0
> >    1     U        The case in question.
> >    U     0        ==> _hw=0 _port=0
> >    U     1        What I was talking about.
> >    0     0        Just like today
> >    1     0        Only cpuid leaves change -- very unlikey
> >    1     1        Full VMware mode
> >    0     1        VMware hyper call mode.
> >
> > The problem here is that vmware_hw is not a boolean and there is
> > currently not a value that lets you know it has not been specified.
> The unspecified value is 0, surely? All of the rows with U under _hw can
> be ignored, I am talking only about _port being a defbool.
You asked Don to add "vmware_hw != 0 => vmware_port ?= 1"  (Where ?= is 
like make, "set if not already set").  Don then naturally thought maybe 
you might want to do the opposite: ("vmware_port != 0 => vmware_hw ?= 
7").  That's what Don is talking about with vmware_hw not being a 
boolean: he can't tell the difference between:
vmware_port=1
vmware_hw=0

and:

vmware_port=1
[nothing about vmware_hw]

In my other e-mail, I suggest that we make vmware_hw the "primary" 
configuration thing, and not even suggest using vmware_port unless they 
want one of the "unusual" configurations.
 -George

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