Re: [Xen-devel] [PATCH v3 2/6] xen: arm: Handle 4K aligned hypervisor load address.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-07-21 at 15:20 +0200, Tim Deegan wrote:
> At 13:59 +0100 on 21 Jul (1405947596), Ian Campbell wrote:
> > +virtphys_clash:
> > +        /* Identity map clashes with boot_third, which we cannot handle 
> > yet */
> > +        PRINT("Unable to build boot page tables - virt and phys addresses 
> > clash.\r\n")
> 
> Please tag this string "- Like so -\r\n" to match the other early output
> from the boot assembler.

OK. (I may do it on commit unless other comments necessitate a resend)

> Presumably we could get around this by making a 4k mapping when the 2M
> mapping would clash (at the cost of some extra code)?  

It might be workable.

We'd have to steal the slot from boot_third to point to 4K worth of 1:1
mapping instead of the expected 4K of virtual mapping and then put back
the virt mapping right after switching to the virtually mapped PC before
we touch anything mapped via that slot i.e. before touching anything
after _end_boot. Doing it at the same time as we establish the fixmap
and dtb mappings would do the trick, I think.

I'd previously concluded this wasn't possible, but don't recall why.
What am I missing this time?

> Not suggesting
> that it's necessary in this version.

Phew!

Ian.


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