Re: [Xen-devel] xen:arm boot failures after commit 1c92a2aa*

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-09-24 at 16:58 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 09/24/2014 03:16 PM, Ian Campbell wrote:
> > On Wed, 2014-09-24 at 05:36 -0700, Suriyan Ramasami wrote:
> > Thanks,
> > 
> >> (XEN)   VTCR_EL2: 80003518
> > 
> > THis has changed from 0x80003558 before this change (sorry, this was in
> > your original report too and I failed to spot it).
> > 
> > The missing bit changes the starting level of the PT from L1 to L2,
> > which ain't gonna work very well ;-).
> > 
> > I can't for the life of me figure out how/why this works on arndale, but
> > it does...
> 
> It also works on Midway (without the patch below). I guess it depends on
> the position of the RAM in the p2m.

I was thinking that presenting a three level PT to an MMU which is
expecting two levels was unlikely to work, but the interesting
properties of the leaf-pte's table bit always being set might mean this
would actually work (sort of) if things were suitably aligned as you are
implying.

I am happy with that theory without digging any further.

Ian.


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