Re: [Xen-devel] [PATCH v2 3/3] x86/setup: remap Xen image up to PFN_DOWN(__pa(_end))

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Thu, Dec 07, 2017 at 05:02:02AM -0700, Jan Beulich wrote:
> >>> On 04.12.17 at 11:24, <daniel.kiper@xxxxxxxxxx> wrote:
> > Current limit, PFN_DOWN(xen_phys_start), introduced by commit b280442
> > (x86: make Xen early boot code relocatable) is not reliable. Potentially
> > its value may fall below PFN_DOWN(__pa(_end))
>
> Under what (perhaps just theoretical) conditions? It seems to imply
> to me that we'd be moved Xen downwards if this was to happen, in
> which case I'd suggest to simply skip the relocation instead (we
> really only ever want to move Xen upwards).

Not always. If __pa(__image_base__) > xen_phys_start and even
if xen_phys_start < __pa(_end) then we are still moving upwards.
That is why we should change the condition. And we have to reference
to something constant not to the moving one.

Daniel

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