Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 2

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-08-13 at 11:13 +0100, Stefano Stabellini wrote:
> 
> > > For example it is only natural for the kernel to try to use the GIC 
> > > hyp
> > > functionalities if they are described, while actually they are not
> > > emulated by Xen at all.
> > 
> > See Ian's earlier reply: It can also be considered natural for it to
> > be aware that when run in EL2 to not use EL1 functionality.

NB EL2 == Hyp and EL1 == Kernel, so it's the other way round, FWIW.

> It is not just about the GIC Hyp functionalities.

What else is there which is not subject to this logic? Timers are too, it
even applies to IOMMU's which have both stage1 and stage2 bits.

BTW, I think kernels _already_ need to deal with a lot of this because in
reality nobody modifies the DTB when they use a firmware which launches the
kernel in EL1. IOW I think the kernel is already aware of which resources
can be used by which privilege level.

Ian.

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