Re: [Xen-devel] Debugging Xen early boot

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

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
> 
> 
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