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




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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