Kexec on arm64

[geoff@infradead.org (Geoff Levand)]

On Thu, 2014-08-07 at 10:59 +0100, Mark Rutland wrote:
> On Thu, Aug 07, 2014 at 01:40:03AM +0100, Geoff Levand wrote:
> > 
> > I haven't looked into it yet, but booting.txt says that the dtb must be
> > 'within the first 512 megabytes from the start of the kernel image'.  If
> > this restriction still holds we can't just put the dtb at
> > text_offset + image_size.
> 
> Isn't that only a problem if text_offset + image_size is huge (510MB+)?

Yes, a limit I don't think we need to be too concerned about at present.

> The wording in booting.txt doesn't sound quite right. As I understand
> it, the 512MB restriction is because of the way we map the dtb in the
> swapper page tables.
> 
> So a better wording would be "the kernel and DTB must be placed in the
> same naturally-aligned 512MB region of memory".
> 
> It should be possible to get rid of the restrictions on the placement of
> the image and DTB, but this requires reworking the VA layout (using a
> kernel text mapping separate from the linear map as with x86_64, and
> similarly having a separate DTB mapping), and unfortunately I haven't
> had the time to do that.

Or maybe just relocate the dtb at startup to within range.

-Geoff