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

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

On Tue, Aug 2, 2016 at 10:11 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
>
>
> On 02/08/16 17:00, Tamas K Lengyel wrote:
>>
>> On Tue, Aug 2, 2016 at 1:38 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
>> Hi Julien,
>> as I said our use-case is purely external so I don't have an actual
>> use-case for anything being accessible from within the guest. However,
>> I could imagine the gfn remapping be used to protect kernel memory
>> areas against information disclosure by only switching to the
>> accessible mapping
>> when certain conditions are met. Also, I had been able to use
>> mem_access from domUs with the use of XSM so I believe it would be
>> possible for a domain to enable mem_access on itself that way and thus
>> not having to implement #VE exactly the way x86 does and still have
>> feature parity.
>
>
> I believe that your suggestion does not currently work. memaccess will pause
> the current vCPU whilst the introspection app will handle the access (see
> p2m_mem_access_check). How can the guest handle the event if the vCPU has
> been paused?
>

True. Not in all cases though - there are async violations - but yea,
that certainly could be a pain.

Tamas

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