Re: [Xen-devel] [PATCH v2 2/2] xen: implement VCPUOP_register_runstate_phys_memory_area

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.05.19 at 13:45, <andrii.anisov@xxxxxxxxx> wrote:
> On 14.05.19 14:24, Julien Grall wrote:
>>>> I think there are an agreement that the two methods should not be used 
>>>> together.
>>>
>>> For a domain or for a particular VCPU?
>>> How should we response on the request to register paddr when we already 
>>> have registered vaddr and vice versa?
>> 
>>  From the discussion with Jan, you would tear down the previous solution and 
>> then
>> register the new version. So this allows cases like a bootloader and a 
> kernel using different version of the interface.
> 
> I'm not sure Jan stated that, he rather questioned that.
> 
> Jan, could you please confirm you agree that it should be dropped already 
> registered runstate and (potentially) changed version in case of the new 
> register request?

Well, I think Julian's implication was that we can't support in particular
the boot loader -> kernel handover case without extra measures (if
at all), and hence he added things together and said what results
from this. Of course ideally we'd reject mixed requests, but unless
someone can come up with a clever means of how to determine entity
boundaries I'm afraid this is not going to be possible without breaking
certain setups.

Jan



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