Re: [Xen-devel] Debugging Xen early boot

["Zytaruk, Kelly" <Kelly.Zytaruk@xxxxxxx>]

Konrad, immediate problem is solved although I don't know why.  I tried putting 
the serial card into a different PCIe slot and it works properly.  Must be 
something wrong with the slot.  I will leave that as a problem for another day.

As for the other question I am still curious as to how to debug early Xen.  How 
was __start_xen written and tested, what sort of tools were used to debug it 
and get it working right?  What do I do in situations where I absolutely can't 
get serial working properly?

Thanks,
Kelly

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Thursday, May 05, 2016 10:20 AM
> To: Zytaruk, Kelly
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Debugging Xen early boot
> 
> On Thu, May 05, 2016 at 01:24:26PM +0000, Zytaruk, Kelly wrote:
> > I am having problems getting XEN boot messages over a serial console.
> >
> > I have two systems.  On one system I can see the XEN boot message over a
> serial console whereas on the other system I cannot.
> >
> > I physically move the same PCIe serial card and hard drive from one system 
> > to
> the other.  One system shows me the Xen boot messages and the other doesn't.
> >
> > My config in /etc/grub.d/20_linux_xen is
> > xen_args="dom0_max_vcpus=4 dom0_mem=2048M,max:3072M iommu=1
> conring_size=16384 loglvl=all guest_loglvl=all com1=115200,8n1,pci
> console=com1"
> >
> > I put a printk at the beginning of the Linux boot and I see the Dom0 Linux 
> > boot
> messages on both systems.  So I know that the serial port works on both
> systems but for some reason I don't see the Xen messages.
> 
> Also, are there any other Serial or Communication devices on the other
> machine? Could you provide the lspci -v from both machines?
> It may be that there is a built-in on the motherboard (like an AMT type 
> thing, or
> IPMI SoL?)
> 
> And if you boot Linux on it, can you do 'dmesg | grep tty' to see what it 
> finds in
> terms of serial cards?
> 
> >
> > I would like to debug through __start_xen to see how the 16550 is being
> initialized.  Is there an easy way to debug __start_xen?
> 
> >
> > Thanks,
> > Kelly
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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