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

[George Dunlap <george.dunlap@eu.citrix.com>]

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