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 13:56
> 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>;
> 'BorisOstrovsky' <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 14:46, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>  -----Original Message-----
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: 07 June 2017 13:00
> >> 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>;
> >> 'BorisOstrovsky' <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 13:55, <Paul.Durrant@xxxxxxxxxx> wrote:
> >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> >> Sent: 07 June 2017 12:50
> >> >> 2) Provide the E820 map of that box.
> >> >> I'm suspecting the BIOS might use an EBDA without recording it in
> >> >> the low BIOS data area. If it's reported in E820 that would then
> >> >> likely be the final kick for us to obey to the E820 map when
> >> >> determining where to put the trampoline.
> >> >>
> >> >
> >> > The stretch kernel booted bare-metal reports:
> >> >
> >> > [    0.000000] e820: BIOS-provided physical RAM map:
> >> > [    0.000000] BIOS-e820: [mem 0x0000000000000000-
> 0x00000000000963ff]
> >> usable
> >> > [    0.000000] BIOS-e820: [mem 0x0000000000096400-
> 0x000000000009ffff]
> >> reserved
> >>
> >> There we go. Subtracting 4k may then even be too little (depending
> >> what EBDA and low memory values the system reports). Of course
> >> it would be a BIOS bug if they reported some memory they use for
> >> themselves through only E820, as that interface is not required to
> >> be present, and really, really old software wouldn't even know
> >> about it and would hence also be in trouble.
> >>
> >
> > Neither 4k nor 8k seemed to be enough. Even subtracting another
> > 64k doesn't work.
> 
> That's rather unexpected.
> 
> > I guess I'm going to have to try to write some code to log values to
> > the VGA buffer to see what is going on.
> 
> Good luck!
> 

That really was too hard... Instead I reverted the patch and stashed EBDA and 
the initial location of the trampoline and dumped them in __start_xen(). The 
EBDA tallies with the E820:

(XEN) boot_ebda = 9640
.
.
(XEN) Xen-e820 RAM map:
(XEN)  0000000000000000 - 0000000000096400 (usable)
(XEN)  0000000000096400 - 00000000000a0000 (reserved)

And the initial location of the trampoline appears to be ok...

(XEN) orig_trampoline_phys = 86000

So, still no clue as to why moving the wakeup code around is messing things up.

  Paul


> Jan


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