Re: [Xen-devel] [PATCH v1 1/2] arm: Add ability to relocate Xen in over 4GB space

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-04-10 at 15:49 +0100, Julien Grall wrote:
> On 10/04/15 15:38, Andrii Anisov wrote:
> > Julien,
> > 
> >>> Secondary CPUs run on unrelocated copy of Xen until turning on MMU.
> >>> After turning on MMU secondary CPUs run on relocated copy of Xen.
> >>
> >> The non-relocated copy of Xen is not marked as reserved. So Xen may
> >> allocate the area for his own purpose before the secondary CPU has boot.
> > 
> > Could you please clarify how the same issue resolved with the piece of
> > bootloader code which implements secondary processors wfe in HYP mode
> > and jump to hypervisor?
> 
> I'm not sure to understand the question.
> 
> Currently, Xen add a bootmodule  (see start_xen) to cover Xen. The base
> address is updated once Xen is relocated.
> 
> You may want to add a bootmodule for the non-relocated Xen.
> 
> I hope it answers to your question.

And if the question is about bootloader code which holds a spinning
secondary CPU then the answer is that this region had better be either
in Secure World only RAM or reserved in the firmware description (i.e.
FDT or ACPI memory map). In FDT that would usually be done via
the /memreserve/ directive, although one cold also imagine fudging the
memory nodes.

Ian.



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