Re: [Xen-devel] Implementing mem-access for PV guests

[Andres Lagar-Cavilla <andreslc@xxxxxxxxxxxxxx>]

> At 01:02 +0000 on 25 Apr (1366851740), Aravindh Puthiyaparambil (aravindp) 
> wrote:
>>>> I'm finally to a point where I can start looking at this more closely.
>>>> I'm trying to wrap my head around the shadow code to figure out the
>>>> right course of action.
>>>> 
>>>> I'd want HVMOP_set_mem_access to work with both shadow and EPT, so
>> 
>> Getting this to work with shadow would allow non-NPT HVM guests to
>> have mem_access support or will this also extend to PV guests?
> 
> It could extend to PV guests as long as you're willing to run them on
> shadow pagetables (i.e. with a significant performance hit).
> 
>> I am interested in getting this to work for PV guests so I was
>> wondering how much extra work that would be. I can definitely help out
>> with this effort.
> 
> I think you'd have to take a good look at the hypercall interface -- PV
> guests have more ways of causing the hypervisor to read and write memory
> for them (e.g. the MMU ops) which wouldn't be intercepted by shadow PTs.
> It certainly ought to be possible, though.

Tim,
wouldn't intercepting all calls to get_page_from_gfn ought to cover it? It 
would also take care of men access not being able to keep track of foreign maps.

Andres

> 
> Tim.


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