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Re: [Xen-users] Always losing the console output after "Scrubbing free

To: Martin Cracauer <cracauer@xxxxxxxx>
Subject: Re: [Xen-users] Always losing the console output after "Scrubbing free RAM"
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Mon, 14 Sep 2009 11:01:09 +0700
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On Mon, Sep 14, 2009 at 7:54 AM, Martin Cracauer <cracauer@xxxxxxxx> wrote:
> Fajar A. Nugraha wrote on Fri, Sep 11, 2009 at 09:47:37AM +0700:
>> Were you able to get Xen to run succesfully with local boot? If not,
>> try it. At least that would help determine whether the problem is
>> Xen/Debian setup, or in mboot/pxe.
> I prepared a regular disk and booted from grub, on the K8T800 chipset
> machine and on a NForce machine.  Same result, the console disappears
> after "scrubbing free RAM" and never comes back.  No change in
> symptoms between pxelinux and grub boots.

Well, this is why I said "One at a time". You're trying to create a
complicated setup without even knowing the basics. I suggest you try
using vendor-bundled Xen first to boot from local disk. Example:
RHEL/Centos5, Opensuse 11.1, Debian Etch.

> I would really appreciate it if you could give these questions a try:

Here's what I got from a 64bit Opensuse 11.1 :

> 1) if I had a dum0 kernel that's just unsuitable (code or config),
> what would the symptoms of trying to boot it be?

(XEN) elf_xen_note_check: ERROR: Will only load images built for the
generic loader or Linux images
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Could not set up DOM0 guest OS
(XEN) ****************************************
(XEN) Reboot in five seconds...

> 2) who's printing "scrubbing free ram", the hypervisor or dom0?

Should be hypervisor. But it only done so after it finds a suitable
kernel to load

(XEN)  Xen  kernel: 64-bit, lsb, compat32
(XEN)  Dom0 kernel: 64-bit, lsb, paddr 0x200000 -> 0x7e20b8
(XEN)  Dom0 alloc.:   0000000078000000->000000007a000000 (465943 pages
to be allocated)
(XEN)  Loaded kernel: ffffffff80200000->ffffffff807e20b8
(XEN)  Init. ramdisk: ffffffff807e3000->ffffffff81339e00
(XEN)  Phys-Mach map: ffffffff8133a000->ffffffff816d80b8
(XEN)  Start info:    ffffffff816d9000->ffffffff816d94b4
(XEN)  Page tables:   ffffffff816da000->ffffffff816e9000
(XEN)  Boot stack:    ffffffff816e9000->ffffffff816ea000
(XEN)  TOTAL:         ffffffff80000000->ffffffff81800000
(XEN)  ENTRY ADDRESS: ffffffff80200000
(XEN) Dom0 has maximum 1 VCPUs
(XEN) Scrubbing Free RAM: .done.

> 2b) speaking of who's printing what, at this point is there any sign
> that dom0 even started doing some work?

Here's the log continuation from (2a)

(XEN) Scrubbing Free RAM: .done.
(XEN) Xen trace buffers: disabled
(XEN) Std. Loglevel: Errors and warnings
(XEN) Guest Loglevel: Nothing (Rate-limited: Errors and warnings)
(XEN) Xen is relinquishing VGA console.
(XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch
input to Xen)
(XEN) Freed 132kB init memory.
Kernel alive
Kernel really alive
Initializing cgroup subsys cpuset
Initializing cgroup subsys cpu
Linux version (geeko@buildhost) (gcc version 4.3.2
[gcc-4_3-branch revision 141291] (SUSE Linux) ) #1 SMP 2008-12-04
18:10:04 +0100
Command line: root=LABEL=ROOT splash=silent showopts console=tty1 console=xvc0

Lines from "Linux version" should be from dom0 kernel. If you don't
have that, probably somehow you don't have the correct console
initialized. Probably incorrect paramater or some missing kernel
compile option. In my case, I setup xen to use serial port 1 as
console, and the kernel uses Xen console (xvc0) and vga (tty1). Here's
the relevant grub.conf entry

title Xen dom0
    root (hd0,1)
    kernel /boot/xen.gz com1=115200,8n1 console=vga,com1 dom0_vcpus_pin
    module /boot/vmlinuz- root=LABEL=ROOT splash=silent
showopts console=tty1 console=xvc0
    module /boot/initrd-

Now it doesn't always need to be THAT complicated. To find out what
parameters you need, it's easier to let your distro setup the correct
parameters first by installing it's version of Xen. After that, you
can modify it up to your needs.


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