Re: [Minios-devel] Single codebase for para-virtualized guests on x86 and ARM?

[Julien Grall <julien.grall@xxxxxxx>]

(+ Stefano and Andre)

On 04/05/2018 04:35 AM, Ajay Garg wrote:
> Hi Julien.
>
> Sorry for restarting this thread, but I was just wondering whether PV
> on ARM might not provide the following benefits :
>
>     * Low overheads as compared to HVM.
I don't buy this argument. The overhead is now quite high because with a 
PV solution as you would need to mitigate meltdown.
Furthermore, this require a lot of changes in your guests and I don't 
see any OS community accepting such burden when virtualization extension 
is getting quite widespread on Arm.
>     * Also support systems/procedures with no hardware-virtualization support.
There was an attempt to get PV support for Arm before the virtualization 
support was added ([1]). But this is dead.
Do you have any platform in mind you would want to run Xen with no 
virtualization extension?
> Of course, the benefits of PV need to be really high, to justify the
> efforts needed to make the required code-changes for PV-support :P
HW virtualization support provides good security and performance with 
limited changes in the guest. Even, x86 community has been discussing to 
deprecate PV and move towards PVH (very similar to Arm guest).
Cheers,

[1] https://wiki.xenproject.org/wiki/Archived/Xen_ARM_(PV)

--
Julien Grall

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