Xen devel - Dec 2008 - pv_ops dom0 and kernel console output problem

Hello list!

I''m trying out pv_ops dom0 patches, and I''m having problems
getting any output
from the kernel to the console. 

grub config:

title dom0-test (2.6.28-rc8-tip)
	root (hd0,0)
	kernel /xen-3.3.gz dom0_mem=512M noreboot loglvl=all guest_loglvl=all
	module /vmlinuz-2.6.28-rc8-tip ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen pci=nomsi
	module /initrd-2.6.28-rc8-tip.img

Is that correct? I''d appreciate comments from people who got it
working..

I can see Xen messages on the (vga) console, but the last line I see is:

(XEN)  Xen is relinquishing VGA console 

I don''t see anything from the actual dom0 kernel.. 

I''m running Xen 3.3.0-2 from Fedora rawhide (includes backported pv_ops
sysfs ballooning support). 

- Is there something else that''s needed from (xen-unstable) hypervisor?
- Or is this problem related only to the pv_ops dom0 kernel?

My Xen hypervisor and dom0 kernel are both 32 bit PAE.

Thanks!

-- Pasi

_______________________________________________
Xen-devel mailing list
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On Fri, Dec 26, 2008 at 01:51:45PM +0200, Pasi Kärkkäinen
wrote:
> Hello list!
> 
> I''m trying out pv_ops dom0 patches, and I''m having
problems getting any output
> from the kernel to the console. 
> 
> grub config:
> 
> title dom0-test (2.6.28-rc8-tip)
> 	root (hd0,0)
> 	kernel /xen-3.3.gz dom0_mem=512M noreboot loglvl=all guest_loglvl=all
> 	module /vmlinuz-2.6.28-rc8-tip ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen pci=nomsi
> 	module /initrd-2.6.28-rc8-tip.img
> 
> Is that correct? I''d appreciate comments from people who got it
working..
> 
> I can see Xen messages on the (vga) console, but the last line I see is:
> 
> (XEN)  Xen is relinquishing VGA console 
> 
> I don''t see anything from the actual dom0 kernel.. 
> 
> I''m running Xen 3.3.0-2 from Fedora rawhide (includes backported
pv_ops
> sysfs ballooning support). 
> 
> - Is there something else that''s needed from (xen-unstable)
hypervisor?
> - Or is this problem related only to the pv_ops dom0 kernel?
> 
> My Xen hypervisor and dom0 kernel are both 32 bit PAE.
> 
# grep XEN .config
CONFIG_XEN=y
CONFIG_XEN_MAX_DOMAIN_MEMORY=32
CONFIG_XEN_SAVE_RESTORE=y
CONFIG_XEN_DEBUG_FS=y
CONFIG_XEN_DOM0=y
CONFIG_XEN_PRIVILEGED_GUEST=y
CONFIG_XEN_DOM0_PCI=y
CONFIG_PCI_XEN=y
CONFIG_XEN_BLKDEV_FRONTEND=y
CONFIG_NETXEN_NIC=m
CONFIG_XEN_NETDEV_FRONTEND=y
CONFIG_XEN_KBDDEV_FRONTEND=y
CONFIG_HVC_XEN=y
CONFIG_XEN_FBDEV_FRONTEND=y
CONFIG_XEN_BALLOON=y
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_XEN_DEV_EVTCHN=y
CONFIG_XEN_BACKEND=y
CONFIG_XEN_BLKDEV_BACKEND=y
CONFIG_XENFS=y
CONFIG_XEN_COMPAT_XENFS=y
CONFIG_XEN_XENBUS_FRONTEND=y

# grep PRINTK .config
CONFIG_PRINTK=y
CONFIG_SND_VERBOSE_PRINTK=y
# CONFIG_PRINTK_TIME is not set
CONFIG_BOOT_PRINTK_DELAY=y
# CONFIG_DYNAMIC_PRINTK_DEBUG is not set
CONFIG_EARLY_PRINTK=y
CONFIG_EARLY_PRINTK_DBGP=y

Dunno if printk stuff is related/needed..

Anyway, do my dom0 kernel settings look correct? Still haven''t figured
out
how to get the kernel console output.. 

-- Pasi

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http://lists.xensource.com/xen-devel

On Fri, Dec 26, 2008 at 01:51:45PM +0200, Pasi Kärkkäinen
wrote:
> Hello list!
> 
> I''m trying out pv_ops dom0 patches, and I''m having
problems getting any output
> from the kernel to the console. 
> 
> grub config:
> 
> title dom0-test (2.6.28-rc8-tip)
> 	root (hd0,0)
> 	kernel /xen-3.3.gz dom0_mem=512M noreboot loglvl=all guest_loglvl=all
> 	module /vmlinuz-2.6.28-rc8-tip ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen pci=nomsi
> 	module /initrd-2.6.28-rc8-tip.img
> 
> Is that correct? I''d appreciate comments from people who got it
working..
> 
> I can see Xen messages on the (vga) console, but the last line I see is:
> 
> (XEN)  Xen is relinquishing VGA console 
> 
> I don''t see anything from the actual dom0 kernel.. 
> 
> I''m running Xen 3.3.0-2 from Fedora rawhide (includes backported
pv_ops
> sysfs ballooning support). 
> 
> - Is there something else that''s needed from (xen-unstable)
hypervisor?
> - Or is this problem related only to the pv_ops dom0 kernel?
> 
> My Xen hypervisor and dom0 kernel are both 32 bit PAE.
> 
> Thanks!
> 
Do you guys have any suggestions? (CC''s added..)

I''ve verified the kernel itself is fine, ie. it boots and works just
fine on
bare metal.. 

-- Pasi

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 11:51 AM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> On Fri, Dec 26, 2008 at 01:51:45PM +0200, Pasi Kärkkäinen wrote:
>> Hello list!
>>
>> I''m trying out pv_ops dom0 patches, and I''m having
problems getting any output
>> from the kernel to the console.
>>
>> grub config:
>>
>> title dom0-test (2.6.28-rc8-tip)
>>       root (hd0,0)
>>       kernel /xen-3.3.gz dom0_mem=512M noreboot loglvl=all
guest_loglvl=all
>>       module /vmlinuz-2.6.28-rc8-tip ro root=/dev/vg00/lv01
console=hvc0 earlyprintk=xen pci=nomsi
>>       module /initrd-2.6.28-rc8-tip.img
>>
>> Is that correct? I''d appreciate comments from people who got
it working..
>>
>> I can see Xen messages on the (vga) console, but the last line I see
is:
>>
>> (XEN)  Xen is relinquishing VGA console
>>
>> I don''t see anything from the actual dom0 kernel..
>>
>> I''m running Xen 3.3.0-2 from Fedora rawhide (includes
backported pv_ops
>> sysfs ballooning support).
>>
>> - Is there something else that''s needed from (xen-unstable)
hypervisor?
>> - Or is this problem related only to the pv_ops dom0 kernel?
>>
>> My Xen hypervisor and dom0 kernel are both 32 bit PAE.
>>
>> Thanks!
>>
>
> Do you guys have any suggestions? (CC''s added..)
>
> I''ve verified the kernel itself is fine, ie. it boots and works
just fine on
> bare metal..
>
Did you add an hvc console to the runlevel?

Cheers,
Todd



-- 
Todd Deshane
http://todddeshane.net
http://runningxen.com

_______________________________________________
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http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 11:55:26AM -0500, Todd Deshane
wrote:
> On Mon, Dec 29, 2008 at 11:51 AM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> > On Fri, Dec 26, 2008 at 01:51:45PM +0200, Pasi Kärkkäinen wrote:
> >> Hello list!
> >>
> >> I''m trying out pv_ops dom0 patches, and I''m
having problems getting any output
> >> from the kernel to the console.
> >>
> >> grub config:
> >>
> >> title dom0-test (2.6.28-rc8-tip)
> >>       root (hd0,0)
> >>       kernel /xen-3.3.gz dom0_mem=512M noreboot loglvl=all
guest_loglvl=all
> >>       module /vmlinuz-2.6.28-rc8-tip ro root=/dev/vg00/lv01
console=hvc0 earlyprintk=xen pci=nomsi
> >>       module /initrd-2.6.28-rc8-tip.img
> >>
> >> Is that correct? I''d appreciate comments from people who
got it working..
> >>
> >> I can see Xen messages on the (vga) console, but the last line I
see is:
> >>
> >> (XEN)  Xen is relinquishing VGA console
> >>
> >> I don''t see anything from the actual dom0 kernel..
> >>
> >> I''m running Xen 3.3.0-2 from Fedora rawhide (includes
backported pv_ops
> >> sysfs ballooning support).
> >>
> >> - Is there something else that''s needed from
(xen-unstable) hypervisor?
> >> - Or is this problem related only to the pv_ops dom0 kernel?
> >>
> >> My Xen hypervisor and dom0 kernel are both 32 bit PAE.
> >>
> >> Thanks!
> >>
> >
> > Do you guys have any suggestions? (CC''s added..)
> >
> > I''ve verified the kernel itself is fine, ie. it boots and
works just fine on
> > bare metal..
> >
> 
> Did you add an hvc console to the runlevel?
> 
Actually, no, I didn''t add hvc console.. That''s a stupid
mistake from me.
Thanks for pointing that out.

Then again, shouldn''t I see kernel messages when it boots up? 

I can only see Xen hypervisor console messages.. nothing from dom0 kernel.. 

-- Pasi

_______________________________________________
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Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 12:02 PM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> On Mon, Dec 29, 2008 at 11:55:26AM -0500, Todd Deshane wrote:
>> Did you add an hvc console to the runlevel?
>>
>
> Actually, no, I didn''t add hvc console.. That''s a stupid
mistake from me.
> Thanks for pointing that out.
>
> Then again, shouldn''t I see kernel messages when it boots up?
>
Is it not writing to /var/log/dmesg|syslog|messages?

Here is some more patches for the hvc stuff that are relatively recent:
http://xen.markmail.org/search/?q=hvc%20list%3Axen-devel#query:hvc%20list%3Axen-devel+page:1+mid:vtzvf44kzapb2vxa+state:results

> I can only see Xen hypervisor console messages.. nothing from dom0 kernel..
>
It does a switch over to the other console.
I would expect xm dmesg to give the xen messages and dmesg to give the
dom0 messages. Could you be losing it when sending it to the serial console?

Adding the hvc console worked for me, if I recall correctly. We should add that
to the wiki as well (if it isn''t there already).

Cheers,
Todd

-- 
Todd Deshane
http://todddeshane.net
http://runningxen.com

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 12:15:01PM -0500, Todd Deshane
wrote:
> On Mon, Dec 29, 2008 at 12:02 PM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> > On Mon, Dec 29, 2008 at 11:55:26AM -0500, Todd Deshane wrote:
> >> Did you add an hvc console to the runlevel?
> >>
> >
> > Actually, no, I didn''t add hvc console.. That''s a
stupid mistake from me.
> > Thanks for pointing that out.
> >
> > Then again, shouldn''t I see kernel messages when it boots up?
> >
> 
> Is it not writing to /var/log/dmesg|syslog|messages?
>
I think it didn''t boot up properly.. I''ll start playing with
it again now,
and check if I''m able to login via network or something.. 
 
> Here is some more patches for the hvc stuff that are relatively recent:
>
http://xen.markmail.org/search/?q=hvc%20list%3Axen-devel#query:hvc%20list%3Axen-devel+page:1+mid:vtzvf44kzapb2vxa+state:results
> 
Thanks for the link.
> 
> > I can only see Xen hypervisor console messages.. nothing from dom0
kernel..
> >
> It does a switch over to the other console.
> I would expect xm dmesg to give the xen messages and dmesg to give the
> dom0 messages. Could you be losing it when sending it to the serial
console?
> 
Actually I''m not using serial console at all.. I only have VGA console.
> Adding the hvc console worked for me, if I recall correctly. We should add
that
> to the wiki as well (if it isn''t there already).
> 
So you could see the dom0 kernel boot messages on (VGA) console, after Xen
messages? 

-- Pasi

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

> Actually I''m not using serial console at all.. I only have VGA
console.
>
>> Adding the hvc console worked for me, if I recall correctly. We should
add that
>> to the wiki as well (if it isn''t there already).
>>
>
> So you could see the dom0 kernel boot messages on (VGA) console, after Xen
> messages?
>
Actually no. I just tested now. The screen goes blank during the dom0 kernel
boot and then shows back up when I get a login: prompt.

I have done most of my testing over a serial console and with the serial
console it shows up.

Jeremy: would you expect this to work? Were there recent patches that
we could be missing?

Cheers,
Todd

-- 
Todd Deshane
http://todddeshane.net
http://runningxen.com

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 12:41:48PM -0500, Todd Deshane
wrote:
> > Actually I''m not using serial console at all.. I only have
VGA console.
> >
> >> Adding the hvc console worked for me, if I recall correctly. We
should add that
> >> to the wiki as well (if it isn''t there already).
> >>
> >
> > So you could see the dom0 kernel boot messages on (VGA) console, after
Xen
> > messages?
> >
> 
> Actually no. I just tested now. The screen goes blank during the dom0
kernel
> boot and then shows back up when I get a login: prompt.
> 
Ok. Good to know. 
> I have done most of my testing over a serial console and with the serial
> console it shows up.
> 
So you get both the Xen and dom0 kernel messages on serial console? 

It would be nice if you could post your grub/xen/kernel settings.. just to
have a working reference. 
> Jeremy: would you expect this to work? Were there recent patches that
> we could be missing?
> 
That would be nice to know too :)

-- Pasi

_______________________________________________
Xen-devel mailing list
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http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 12:49 PM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> On Mon, Dec 29, 2008 at 12:41:48PM -0500, Todd Deshane wrote:
>> > Actually I''m not using serial console at all.. I only
have VGA console.
>> >
>> >> Adding the hvc console worked for me, if I recall correctly.
We should add that
>> >> to the wiki as well (if it isn''t there already).
>> >>
>> >
>> > So you could see the dom0 kernel boot messages on (VGA) console,
after Xen
>> > messages?
>> >
>>
>> Actually no. I just tested now. The screen goes blank during the dom0
kernel
>> boot and then shows back up when I get a login: prompt.
>>
>
> Ok. Good to know.
>
>> I have done most of my testing over a serial console and with the
serial
>> console it shows up.
>>
>
> So you get both the Xen and dom0 kernel messages on serial console?
>
> It would be nice if you could post your grub/xen/kernel settings.. just to
> have a working reference.
>
title           Xen 3.4-unstable DEBUG/ Ubuntu 8.10, kernel 2.6.28-rc7-tip
root            (hd0,0)
kernel          /boot/xen-3.4-unstable.gz loglvl=all guest_loglvl=all
com1=115200,8n1 console=com1
module          /boot/vmlinuz-2.6.28-rc7-tip root=/dev/sda1 ro
console=hvc0 earlyprintk=xen xencons=ttyS0,115200 pci=nomsi
module          /boot/initrd.img-2.6.28-rc7-tip

The rest of what I have found I have tried to post here:
http://wiki.xensource.com/xenwiki/XenParavirtOps

Hope that helps.
>> Jeremy: would you expect this to work? Were there recent patches that
>> we could be missing?
>>
>
> That would be nice to know too :)
>
> -- Pasi
>


-- 
Todd Deshane
http://todddeshane.net
http://runningxen.com

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Mon, Dec 29, 2008 at 12:55:42PM -0500, Todd Deshane
wrote:
> On Mon, Dec 29, 2008 at 12:49 PM, Pasi Kärkkäinen <pasik@iki.fi>
wrote:
> > On Mon, Dec 29, 2008 at 12:41:48PM -0500, Todd Deshane wrote:
> >> > Actually I''m not using serial console at all.. I
only have VGA console.
> >> >
> >> >> Adding the hvc console worked for me, if I recall
correctly. We should add that
> >> >> to the wiki as well (if it isn''t there already).
> >> >>
> >> >
> >> > So you could see the dom0 kernel boot messages on (VGA)
console, after Xen
> >> > messages?
> >> >
> >>
> >> Actually no. I just tested now. The screen goes blank during the
dom0 kernel
> >> boot and then shows back up when I get a login: prompt.
> >>
> >
> > Ok. Good to know.
> >
> >> I have done most of my testing over a serial console and with the
serial
> >> console it shows up.
> >>
> >
> > So you get both the Xen and dom0 kernel messages on serial console?
> >
> > It would be nice if you could post your grub/xen/kernel settings..
just to
> > have a working reference.
> >
> 
> title           Xen 3.4-unstable DEBUG/ Ubuntu 8.10, kernel 2.6.28-rc7-tip
> root            (hd0,0)
> kernel          /boot/xen-3.4-unstable.gz loglvl=all guest_loglvl=all
> com1=115200,8n1 console=com1
> module          /boot/vmlinuz-2.6.28-rc7-tip root=/dev/sda1 ro
> console=hvc0 earlyprintk=xen xencons=ttyS0,115200 pci=nomsi
> module          /boot/initrd.img-2.6.28-rc7-tip
> 
> The rest of what I have found I have tried to post here:
> http://wiki.xensource.com/xenwiki/XenParavirtOps
> 
> Hope that helps.
> 
Thanks!

I wonder if it''s about that "xencons=" option for the
kernel.. I don''t have
that at all. 

Let''s see what happens when I get to try those. 

-- Pasi

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Todd Deshane wrote:
> Actually no. I just tested now. The screen goes blank during the dom0
kernel
> boot and then shows back up when I get a login: prompt.
>
> I have done most of my testing over a serial console and with the serial
> console it shows up.
>
> Jeremy: would you expect this to work? Were there recent patches that
> we could be missing?
>   
Nothing I can think of; it works for me.  I don''t have my test machine 
on hand, so I''m not sure what the exact kernel command line is.  But 
perhaps booting without "console=hvc0" would work, and
"earlyprintk=vga".

    J

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On Tue, Dec 30, 2008 at 10:02:18PM +1100, Jeremy Fitzhardinge
wrote:
> Todd Deshane wrote:
> >Actually no. I just tested now. The screen goes blank during the dom0 
> >kernel
> >boot and then shows back up when I get a login: prompt.
> >
> >I have done most of my testing over a serial console and with the
serial
> >console it shows up.
> >
> >Jeremy: would you expect this to work? Were there recent patches that
> >we could be missing?
> >  
> 
> Nothing I can think of; it works for me.  I don''t have my test
machine
> on hand, so I''m not sure what the exact kernel command line is. 
But
> perhaps booting without "console=hvc0" would work, and
"earlyprintk=vga".
> 
Thanks!

"earlyprintk=vga" solved the problem.. now I can see pv_ops dom0
kernel boot
messages on the VGA console after Xen hypervisor messages.

-- Pasi

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http://lists.xensource.com/xen-devel

On Tue, Dec 30, 2008 at 03:07:03PM +0200, Pasi Kärkkäinen
wrote:
> On Tue, Dec 30, 2008 at 10:02:18PM +1100, Jeremy Fitzhardinge wrote:
> > Todd Deshane wrote:
> > >Actually no. I just tested now. The screen goes blank during the
dom0
> > >kernel
> > >boot and then shows back up when I get a login: prompt.
> > >
> > >I have done most of my testing over a serial console and with the
serial
> > >console it shows up.
> > >
> > >Jeremy: would you expect this to work? Were there recent patches
that
> > >we could be missing?
> > >  
> > 
> > Nothing I can think of; it works for me.  I don''t have my
test machine
> > on hand, so I''m not sure what the exact kernel command line
is.  But
> > perhaps booting without "console=hvc0" would work, and
"earlyprintk=vga".
> > 
> 
> Thanks!
> 
> "earlyprintk=vga" solved the problem.. now I can see pv_ops dom0
kernel boot
> messages on the VGA console after Xen hypervisor messages.
> 
Or actually.. 

I can see the pv_ops dom0 kernel detect and print the (Xen) memory layout for
dom0, then some misc information and then the console is cleared and nothing
happens anymore.. I''m not sure if it gets to initrd yet at that point..
at
least I don''t see any disk activity (based on the hdd LED).

My grub configuration atm:

title dom0-test (2.6.28-rc8-tip)
	root (hd0,0)
	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all
	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01 earlyprintk=vga
pci=nomsi
	module /initrd-2.6.28-rc8-tip.img

What is "earlyprintk=xen" supposed to do? 

-- Pasi

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On Tue, Dec 30, 2008 at 03:20:36PM +0200, Pasi Kärkkäinen
wrote:
> On Tue, Dec 30, 2008 at 03:07:03PM +0200, Pasi Kärkkäinen wrote:
> > On Tue, Dec 30, 2008 at 10:02:18PM +1100, Jeremy Fitzhardinge wrote:
> > > Todd Deshane wrote:
> > > >Actually no. I just tested now. The screen goes blank during
the dom0
> > > >kernel
> > > >boot and then shows back up when I get a login: prompt.
> > > >
> > > >I have done most of my testing over a serial console and with
the serial
> > > >console it shows up.
> > > >
> > > >Jeremy: would you expect this to work? Were there recent
patches that
> > > >we could be missing?
> > > >  
> > > 
> > > Nothing I can think of; it works for me.  I don''t have
my test machine
> > > on hand, so I''m not sure what the exact kernel command
line is.  But
> > > perhaps booting without "console=hvc0" would work, and
"earlyprintk=vga".
> > > 
> > 
> > Thanks!
> > 
> > "earlyprintk=vga" solved the problem.. now I can see pv_ops
dom0 kernel boot
> > messages on the VGA console after Xen hypervisor messages.
> > 
> 
> Or actually.. 
> 
> I can see the pv_ops dom0 kernel detect and print the (Xen) memory layout
for
> dom0, then some misc information and then the console is cleared and
nothing
> happens anymore.. I''m not sure if it gets to initrd yet at that
point.. at
> least I don''t see any disk activity (based on the hdd LED).
> 
> My grub configuration atm:
> 
> title dom0-test (2.6.28-rc8-tip)
> 	root (hd0,0)
> 	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all
> 	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01 earlyprintk=vga
pci=nomsi
> 	module /initrd-2.6.28-rc8-tip.img
> 
> What is "earlyprintk=xen" supposed to do? 
> 
I still haven''t gotten VGA console to work, but now _serial_ console
seems to work
using this configuration:

title dom0-test (2.6.28-rc8-tip) / serial console
	root (hd0,0)
	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all com1=19200,8n1
console=com1
	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen xencons=ttyS0,19200 pci=nomsi
	module /initrd-2.6.28-rc8-tip.img

I was able to capture the pv_ops dom0 kernel crashes using serial console..
I''ll post another thread about that.

-- Pasi

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On Tue, Dec 30, 2008 at 03:20:36PM +0200, Pasi Kärkkäinen
wrote:
>
> What is "earlyprintk=xen" supposed to do? 
> 
Reading pv_ops wiki page I noticed this:

"If the domain crashes very early, before any output appears on the
console,
then booting with: "earlyprintk=xen" should provide some useful
information.
If you are running a debug build of Xen hypervisor (set "debug = y" in
Config.mk in the Xen source tree), then you should get crash dumps on the
Xen console. You can view those with "xm dmesg"."

So I guess earlyprintk=xen is only useful if you''re running debug build
of
Xen hypervisor.. ?

-- Pasi

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Pasi Kärkkäinen wrote:
> Reading pv_ops wiki page I noticed this:
>
> "If the domain crashes very early, before any output appears on the
console,
> then booting with: "earlyprintk=xen" should provide some useful
information.
> If you are running a debug build of Xen hypervisor (set "debug =
y" in
> Config.mk in the Xen source tree), then you should get crash dumps on the
> Xen console. You can view those with "xm dmesg"."
>
> So I guess earlyprintk=xen is only useful if you''re running debug
build of
> Xen hypervisor.. ?
earlyprintk=xen has the effect of directing the kernel''s console output
via the console output hypercall.  domU kernel''s are not generally 
allowed to do this, but it is when you compile Xen in debug mode.  dom0, 
however, uses the Xen console in the normal case, so it doesn''t need a 
debug Xen build.  But when Xen switches its console output to serial the 
kernel''s output goes with it, so if you want it to appear on VGA you 
need to use the VGA console output (make sure your kernel has all the VT 
console options enabled).

    J

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On Wed, Dec 31, 2008 at 09:44:52AM +1100, Jeremy Fitzhardinge
wrote:
> Pasi Kärkkäinen wrote:
> >Reading pv_ops wiki page I noticed this:
> >
> >"If the domain crashes very early, before any output appears on
the
> >console,
> >then booting with: "earlyprintk=xen" should provide some
useful
> >information.
> >If you are running a debug build of Xen hypervisor (set "debug =
y" in
> >Config.mk in the Xen source tree), then you should get crash dumps on
the
> >Xen console. You can view those with "xm dmesg"."
> >
> >So I guess earlyprintk=xen is only useful if you''re running
debug build of
> >Xen hypervisor.. ?
> 
> earlyprintk=xen has the effect of directing the kernel''s console
output
> via the console output hypercall.  domU kernel''s are not generally
> allowed to do this, but it is when you compile Xen in debug mode.  dom0, 
> however, uses the Xen console in the normal case, so it doesn''t
need a
> debug Xen build.  But when Xen switches its console output to serial the 
> kernel''s output goes with it, so if you want it to appear on VGA
you
> need to use the VGA console output (make sure your kernel has all the VT 
> console options enabled).
> 
Thanks for clearing that up!

-- Pasi

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On Tue, Dec 30, 2008 at 04:18:13PM +0200, Pasi Kärkkäinen
wrote:
> On Tue, Dec 30, 2008 at 03:20:36PM +0200, Pasi Kärkkäinen wrote:
> > On Tue, Dec 30, 2008 at 03:07:03PM +0200, Pasi Kärkkäinen wrote:
> > > On Tue, Dec 30, 2008 at 10:02:18PM +1100, Jeremy Fitzhardinge
wrote:
> > > > Todd Deshane wrote:
> > > > >Actually no. I just tested now. The screen goes blank
during the dom0
> > > > >kernel
> > > > >boot and then shows back up when I get a login: prompt.
> > > > >
> > > > >I have done most of my testing over a serial console and
with the serial
> > > > >console it shows up.
> > > > >
> > > > >Jeremy: would you expect this to work? Were there recent
patches that
> > > > >we could be missing?
> > > > >  
> > > > 
> > > > Nothing I can think of; it works for me.  I don''t
have my test machine
> > > > on hand, so I''m not sure what the exact kernel
command line is.  But
> > > > perhaps booting without "console=hvc0" would work,
and "earlyprintk=vga".
> > > > 
> > > 
> > > Thanks!
> > > 
> > > "earlyprintk=vga" solved the problem.. now I can see
pv_ops dom0 kernel boot
> > > messages on the VGA console after Xen hypervisor messages.
> > > 
> > 
> > Or actually.. 
> > 
> > I can see the pv_ops dom0 kernel detect and print the (Xen) memory
layout for
> > dom0, then some misc information and then the console is cleared and
nothing
> > happens anymore.. I''m not sure if it gets to initrd yet at
that point.. at
> > least I don''t see any disk activity (based on the hdd LED).
> > 
> > My grub configuration atm:
> > 
> > title dom0-test (2.6.28-rc8-tip)
> > 	root (hd0,0)
> > 	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all
> > 	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01
earlyprintk=vga pci=nomsi
> > 	module /initrd-2.6.28-rc8-tip.img
> > 
> > What is "earlyprintk=xen" supposed to do? 
> > 
> 
> I still haven''t gotten VGA console to work, but now _serial_
console seems to work
> using this configuration:
> 
> title dom0-test (2.6.28-rc8-tip) / serial console
> 	root (hd0,0)
> 	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all
com1=19200,8n1 console=com1
> 	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen xencons=ttyS0,19200 pci=nomsi
> 	module /initrd-2.6.28-rc8-tip.img
> 
Actually xencons= doesn''t seem to be needed for the Linux kernel.

So here''s more simple working grub configuration for using serial
console
with Xen and pv_ops dom0 kernel:


title dom0-test (2.6.28-rc8-tip) / serial console
	root (hd0,0)
	kernel /xen-3.3.gz dom0_mem=1024M loglvl=all guest_loglvl=all com1=19200,8n1
console=com1
	module /vmlinuz-2.6.28-rc8-tip.gz ro root=/dev/vg00/lv01 console=hvc0
earlyprintk=xen pci=nomsi
	module /initrd-2.6.28-rc8-tip.img


That works for me. 

-- Pasi

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