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

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 09/24/14 12:44, George Dunlap wrote:
> On 09/24/2014 05:31 PM, 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
> >
> >
> > > > > If yes then I still think you would want to set the default based on
> > > > > vmware-hw, wouldn't you?
> > > > I guess so since this is a BOOLEAN.
> > > defbool I hope.
> > 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.
> >
> > 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.
> >
> > So I think it is just more confusing to have vmware_hw change
> > the default of vmware_port but the inverse is not true.
> So is it the case that if you specify vmware_hw with a value that your 
> guest isn't expecting, it may not work?
That is not the case for all versions of Linux I have tested with. And
since viridian should be set for windows (which hides the vmware_hw
setting), I do not expect this to be true.  Clearly someone could
write new code that fails because of this.


> I think the main thing Ian wants is probably a simple way for people 
> to just turn everything on.  Having vmware_hw!=0 => vmware_port 
> defaults to 1 seems like a reasonable way to do that.
> We could almost think of vmware_port as an "advanced" option that most 
> people don't need to set: i.e., you only need to set it if you want 
> one of the "unusual" modes (like CPUID-only or hypercall-only).
Ah, that makes sense.  Will do it.

   -Don Slutz


>  -George

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