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

[Julien Grall <julien.grall@xxxxxxx>]

Hello Sergej,

Please try to reply to all when answering on the ML. Otherwise the 
answer may be delayed/lost.
On 03/08/16 13:45, Sergej Proskurin wrote:
> The interesting part about #VE is that it allows to handle certain
> violations (currently limited to EPT violations -- future
> implementations might introduce also further violations) inside of the
> guest, without the need to explicitly trap into the VMM. Thus, #VE allow
> switching of different memory views in-guest. Because of this, I also
> agree that event channels would suffice in our case, since we do not
> have sufficient hardware support on ARM and would need to trap into the
> VMM anyway.
The cost of doing an hypercall on ARM is very small compare to x86 (~1/3 
of the number of x86 cycles) because we don't have to save all the state 
every time. So I am not convinced by the argument of limiting the number 
of trap to the hypervisor and allow a guest to play with altp2m on ARM.
I will have to see a concrete example before going forward with the 
event channel.
Regards,

--
Julien Grall

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