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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Julien Grall [mailto:julien.grall@xxxxxxx]
> Sent: 06 June 2017 18:41
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; 'Jan Beulich'
> <JBeulich@xxxxxxxx>
> Cc: xen-devel (xen-devel@xxxxxxxxxxxxxxxxxxxx) <xen-
> devel@xxxxxxxxxxxxxxxxxxxx>
> Subject: Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot
> 
> Hi Paul,
> 
> On 06/06/17 16:51, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: 06 June 2017 16:11
> >> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> >> Cc: xen-devel (xen-devel@xxxxxxxxxxxxxxxxxxxx) <xen-
> >> devel@xxxxxxxxxxxxxxxxxxxx>
> >> Subject: Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot
> >>
> >>>>> On 06.06.17 at 16:32, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>> I've been having fun setting up a new test rig...
> >>>
> >>> I have a skull canyon NUC and I put debian stretch (rc4) on it (so that's 
> >>> a
> >>> 4.9 kernel) and then tried building and installing the latest Xen staging-
> 4.9
> >>> code. The system failed to boot... basically it got stuck before even
> >>> managing to get sufficiently into Xen to spit out anything on the console.
> >>> Xen 4.8 OTOH booted just fine so I started bisecting and after 14
> iterations
> >>> I got down to the following commit is being the problem:
> >>>
> >>> commit c0655e492e6b33e26ec9cd33f59725d0db89cdd0
> >>> Author: Juergen Gross <jgross@xxxxxxxx>
> >>> Date:   Fri Mar 24 14:18:54 2017 +0100
> >>>
> >>>     x86: split boot trampoline into permanent and temporary part
> >>>
> >>>     The hypervisor needs a trampoline in low memory for early boot and
> >>>     later for bringing up cpus and during wakeup from suspend. Today this
> >>>     trampoline is kept completely even if most of it isn't needed later.
> >>>
> >>>     Split the trampoline into a permanent part and a temporary part
> needed
> >>>     at early boot only. Introduce a new entry at the boundary.
> >>>
> >>>     Reduce the stack for wakeup code in order for the permanent
> >>>     trampoline to fit in a single page. 4k of stack seems excessive, about
> >>>     3k should be more than enough.
> >>>
> >>>     Add an ASSERT() to the linker script to ensure the wakeup stack is
> >>>     always at least 3k.
> >>>
> >>>     Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >>>     Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> >>>
> >>> To verify this I checked out master, reverted that commit, and tried
> again.
> >>> The NUC still booted fine.
> >>
> >> Well, interesting, but I don't think it is very realistic to expect any
> >> fix with just the information you supply. There must be something
> >> rather special about that system, and likely it would help if we
> >> knew what that is. E.g. an unusual E820 map. Worse would be if
> >> they used memory outside of properly marked E820 regions in a
> >> way colliding with what we do.
> >>
> >> Otherwise I'm afraid we need to hope for you to debug the issue.
> >>
> >
> > Yes, I was posting this more a heads-up for the moment, so that 4.9 does
> not go out with this regression.
> 
> I would have appreciated to be CCed in this e-mail as this concern 4.9
> release... Please take the habit to CC the release manager for anything
> targeting a release.
> 

Yes, sorry I should have cc-ed... I was in a bit of a rush and forgot.

  Cheers,

    Paul

> Cheers,
> 
> --
> Julien Grall
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