Re: [Xen-devel] [PATCH v6] altp2m: Introduce external-only and limited use-cases

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.04.17 at 10:52, <george.dunlap@xxxxxxxxxx> wrote:
> On 05/04/17 18:41, Tamas K Lengyel wrote:
>> On Wed, Apr 5, 2017 at 9:04 AM, George Dunlap <george.dunlap@xxxxxxxxxx> 
>> wrote:
>>> On Tue, Apr 4, 2017 at 4:24 PM, Tamas K Lengyel
>>> <tamas.lengyel@xxxxxxxxxxxx> wrote:
>>> "mixed"
>>>
>>> Both external domains and the guest itself have full access to altp2m
>>> functionality
>>>
>>> "limited"
>>>
>>> External domains have access to full altp2m functionality; guest has
>>> access only to HVMOP_altp2m_vcpu_enable_notify (ability to enable
>>> VMFUNC and #VE features).
> [snip]
>>> Out of curiosity, what's the use case of the "mixed" mode?
>> 
>> It's not entirely clear but that has been the mode that it was introduced 
>> with.
> 
> Actually I had some sort of a weird typo there... What I meant to ask
> about was actually "limited" mode: if the guest can't modify its own p2m
> tables, what's the use of a #VE?

While this may not be as it works today, I'd expect "cannot change
its altp2m-s" to neither imply in can't use VMFUNC to switch between
them nor to extend to being able to set/clear the suppress-VE bit
(which isn't permission bit after all).

Jan


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