Re: [Xen-devel] [PATCH v2 00/25] arm/altp2m: Introducing altp2m to ARM.

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Wed, Aug 3, 2016 at 12:16 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>
>
> On 03/08/16 19:11, Tamas K Lengyel wrote:
>>
>> On Wed, Aug 3, 2016 at 11:56 AM, Julien Grall <julien.grall@xxxxxxx>
>> wrote:
>>>
>>>
>>>
>>> On 03/08/16 18:51, Tamas K Lengyel wrote:
>>>>
>>>>
>>>> On Wed, Aug 3, 2016 at 11:45 AM, Julien Grall <julien.grall@xxxxxxx>
>>>> wrote:
>>>>>
>>>>>
>>>>> The whole discussion of this series was to defer the exposition of
>>>>> altp2m
>>>>> HVMOP to the guest until we find a usage. I.e a simple:
>>>>>
>>>>> xsm_hvm_altp2m_op(XSM_PRIV/XSM_DM_PRIV, d);
>>>>>
>>>>> So why do you want to re-invent a new interface here?
>>>>
>>>>
>>>>
>>>> I guess I misinterpreted your request of not having this interface
>>>> exposed to the guest. If we are fine with exposing the interface to
>>>> the guest but having XSM manage whether it's allowed by default I'm
>>>> certainly OK with that.
>>>
>>>
>>>
>>> By default the interface will not be exposed to the guest.
>>> XSM_PRIV/XSM_DM_PRIV only allow a privileged domain or a device model
>>> domain
>>> to use the interface. The guest will not be enabled to access it.
>>
>>
>> Yes. I guess our terminology differs about what we mean by "exposed".
>> In my book if the interface is available to the guest but access
>> attempts are denied by XSM that means the interface is exposed but
>> restricted.
>
>
> Although the behavior is very different compare to what x86 does. By default
> the guest will be able to play with altp2m.

Personally my life would be a lot easier on x86 too if the default XSM
behavior was external-use only for altp2m. Or if at last XSM was
turned on by default..

Tamas

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