Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 07 June 2017 13:19
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: Julien Grall (julien.grall@xxxxxxx) <julien.grall@xxxxxxx>; Andrew
> Cooper <Andrew.Cooper3@xxxxxxxxxx>; xen-devel (xen-
> devel@xxxxxxxxxxxxxxxxxxxx) <xen-devel@xxxxxxxxxxxxxxxxxxxx>; 'Boris
> Ostrovsky' <boris.ostrovsky@xxxxxxxxxx>; Juergen Gross
> <jgross@xxxxxxxx>
> Subject: RE: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot
> 
> >>> On 07.06.17 at 14:02, <Paul.Durrant@xxxxxxxxxx> wrote:
> >> From: Juergen Gross [mailto:jgross@xxxxxxxx]
> >> Sent: 07 June 2017 12:57
> >>
> >> On 07/06/17 13:06, Paul Durrant wrote:
> >> > It appears that it is just the code that needs to go at the end. The
> following
> >> patch is sufficient to avoid the problem. This may be preferable to a full
> >> reversion...
> >>
> >> I believe this is wrong. You risk the wakeup_stack extending into wakeup
> >> code and the main reason of the patch is gone, as now the permanent
> >> trampoline no longer is on a single page.
> >>
> >
> > I must be misunderstanding something then. The stack grows down from
> > wakeup_stack towards wakeup_stack_start doesn't it? So why would
> there be an
> > issue with the stack overwriting wakeup code?
> 
> I think this is a pointless discussion: Once we know memory is being
> corrupted, it doesn't help shuffling things around. By putting the
> wakeup code at the end, it'll be that which gets corrupted, and
> hence S3 wakeup would not work. We can really only try to figure
> out what parts of memory we need to avoid touching _at all_.
> 

Yes, fair enough. I'm currently trying to figure out what the code in head.S 
just ahead of trampoline_setup is trying to do.

  Paul

> Jan


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