Re: [Xen-devel] [PATCH v8 4/7] xen: Add vmware_port support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.02.15 at 20:30, <dslutz@xxxxxxxxxxx> wrote:
> While coding this is up I have hit issues that I need input on:
> 
> As a HVM_PARAM_ item, I would assume I should be following
> what HVM_PARAM_VIRIDIAN does.  It has this comment:
> 
>             case HVM_PARAM_VIRIDIAN:
>                 /* This should only ever be set once by the tools and
> read by the guest. */
> 
> Which is almost true.  However the code allows you to change from 0 to
> non-zero any time in the life of the DomU.  I am assuming that this is
> why xc_domain_save() and xc_domain_restore() save and restore this
> HVM_PARAM_ item.
> 
> With the enable of vmware_port the same way, I feel it would be a bug
> to allow the enable after "create" to not also adjust QEMU.  Currently
> there is no way for the hypervisor to tell QEMU to enable vmware_port
> handling.  So to avoid adding this code to xen and QEMU, it looks to
> me that adding code to make this a true write only 1 time would be
> needed so that you cannot use the hyper call to change later.
> 
> So, should I extend this change to cover other HVM_PARAM_?
> 
> Is all this additional code (xc_domain_save(), xc_domain_restore(),
> write only 1 time) still better then a domain_create() flag?

I suppose for your case it's indeed the right approach. Which other
params this may be true for as well I can't immediately say, but I'd
certainly like to ask for adjustments to others to be in separate
patches (and perhaps even a separate series), with proper
rationale for each of them. I guess Andrew will have further input
for you on this matter...

Jan


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