Re: [Xen-devel] About runtime service for Xen on ARM

[Shannon Zhao <shannon.zhao@xxxxxxxxxx>]

Hi Julien,

Thanks for your reply. :)

On 2015/8/26 11:24, Julien Grall wrote:
> On 19/08/2015 23:27, Shannon Zhao wrote:
> > Hi Julien,
> Hi Shannon,
>
> Sorry for the late answer I was on holiday. In general it's better to CC
> multiple person and the mailing list as we may not be able to answer in
> short time or not know the answer.
>
> I've CCed the ML and few people which know better than me the status of
> EFI runtime.
>
> > Do you know the status of runtime service for Xen on ARM? Does it
> > support runtime service booting with DT? If not, is there a plan to
> > support it?
> There is no support of runtime EFI on ARM for now and I'm not aware of
> any short plan for this.
>
> > In addition, if you know this, does it support runtime service for Xen
> > on x86?
> There is some on-going work for EFI runtime on x86. I'm not sure if it
> has been upstream (CCed Daniel for this).
>
> Although, one of there is a fundamental difference between the UEFI boot
> on x86 and ARM. While the code is the same, on ARM the UEFI act as a
> stub and should not be able to communicate via exported variable with
> Xen (we clobber BSS just after the UEFI stub jump on the normal boot
> start).
>
> I know that the ARM EFI stub is using some shared variable with Xen (I
> have in mind the memory banks see bootinfo). We are very lucky that it's
> working because the variable is living in initdata which somehow is part
> of text (I'm not sure why) and not BSS.
> So we should either decide that the stub and xen should be able to
> communicate together or not.
>
> I would be in favor of the former but I don't know what are the view of
> the others.
>
> Regards,
--
Shannon

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