Re: [PATCH V7] x86/altp2m: Hypercall to set altp2m view visibility

[Jan Beulich <jbeulich@xxxxxxxx>]

On 31.03.2020 09:54, Isaila Alexandru wrote:
> 
> 
> On 31.03.2020 10:43, Jan Beulich wrote:
>> On 30.03.2020 08:54, Alexandru Isaila wrote:
>>> At this moment a guest can call vmfunc to change the altp2m view. This
>>> should be limited in order to avoid any unwanted view switch.
>>>
>>> The new xc_altp2m_set_visibility() solves this by making views invisible
>>> to vmfunc.
>>> This is done by having a separate arch.altp2m_working_eptp that is
>>> populated and made invalid in the same places as altp2m_eptp. This is
>>> written to EPTP_LIST_ADDR.
>>> The views are made in/visible by marking them with INVALID_MFN or
>>> copying them back from altp2m_eptp.
>>> To have consistency the visibility also applies to
>>> p2m_switch_domain_altp2m_by_id().
>>>
>>> The usage of this hypercall is aimed at dom0 having a logic with a number 
>>> of views
>>> created and at some time there is a need to be sure that only some of the 
>>> views
>>> can be switched, saving the rest and making them visible when the time
>>> is right.
>>>
>>> Note: If altp2m mode is set to mixed the guest is able to change the view
>>> visibility and then call vmfunc.
>>>
>>> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
>>
>> For v6 I did provide a hypervisor side R-b; I didn't think ...
> 
> No you didn't.

https://lists.xenproject.org/archives/html/xen-devel/2020-03/msg00145.html

Jan