Re: Xen on Intel Atom E3815: crash, no output

[Alexey G <x1917x@gmail.com>]

Hi Stefano,

On Mon, 31 Jul 2017 16:39:37 -0700 (PDT)
Stefano Stabellini <sstabellini@kernel.org> wrote:

> I noticed that Xen does not boot on Intel Atom E3815. The system is a
> Dell Edge Gateway 3003:
> 
> http://i.dell.com/sites/doccontent/shared-content/data-sheets/en/Documents/Dell_Edge_Gateway_3000_Series_spec_sheet.pdf?newtab=true
> 
> Grub2 loads Xen and Dom0, but no output comes out of Xen. After the
> "Loading" messages from Grub2, Xen doesn't manage to print even a single
> character and the system obviously crashes, but I don't know why because
> there is no output. Before you ask, no I don't have a serial on the
> system.
> 
> I tried to pass console=vga vga=text-80x25 and console=vga vga=ask, but
> I still got nothing.
> 
> Do you have any ideas how to get some output on the screen? Do you know
> how to get Xen to boot successfully?

I remember using KBC LEDs to debug a similar issue (not Xen-related) with
no screen output available. Three LEDs with an easy I/O interface to control
them are quite useful for blind debugging.

If the system in question support SMI emulation of legacy KBC I/O ports
(Atom E38xx itself has support for it, so it's up to system BIOS to have
support for USB legacy emulation), you can try using KBC LEDs too or some
other LEDs, if neither screen output nor serial debugging is possible.

AFAIR there are not many initialization stages take place before VGA console
output starts, so finding out which initialization step fails maybe
enough to debug the issue.

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