Re: blank screen VGA or Serial while linux boot

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Dec 28, 2016 at 03:17:20PM +0100, Daniele Palumbo wrote:
> Hi,
> 
> Sorry for bothering, I am following
> https://wiki.xenproject.org/wiki/Xen_Serial_Console
> and
> http://www-archive.xenproject.org/files/xensummit_4/xensummit_linux_console_slides.pdf
> 
> And as written in
> https://wiki.xenproject.org/wiki/XenParavirtOps
> Here i am writing.
> 
> My goal is to have the same console output on VGA and internal serial port.
> 
> I am on gentoo, with Xen 4.6.4, custom kernel.
> My kernel config is in attachment.
> 
> Test hardware is a Sun x4150, with ILOm.
> Serial speed is set to 9600 bps, with console redirection (so all of the BIOS messages are shown).
> 
> See an example of my output in attachment (serial_out.txt), with the following settings:
> GRUB_TERMINAL="console serial"
> GRUB_SERIAL_COMMAND="serial --speed=9600 --unit=1 --word=8 --parity=no --stop=1"
> GRUB_CMDLINE_XEN="loglvl=all guest_loglvl=all com1=9600,8n1 console=com1,vga"
> GRUB_CMDLINE_LINUX="xencons=xvc console=xvc0 console=hvc0 console=tty1 earlyprintk=xen nomodeset"

You can remove the 'xencons' and 'console=xvc0'

> full grub.cfg in attachment.
> 
> 
> As by the logs I am able to see the same terminal from BIOS to the XEN multiboot.
> With xen multiboot i mean messages starting with
> "(XEN) "
> e.g.:
> (XEN) Video information:Gentoo GNU/Linux (with Xen hypervisor)
> (XEN)  VGA is text mode 80x25, font 8x16
> 
> I am not able to get the same message across serial _AND_ vga terminal upon boot,
> AFTER the xen multiboot.
> 
> With earlyprintk=xen i see also linux messages starting with
> "[    0.000000] "
> e.g., last line seen is
> [    0.000000] Memory: 925860K/2097148K available (5475K kernel code, 570K rwdata, 2344K rodata, 992K init, 1
> 
> After that, i can always see the login prompt in both serial and VGA output.
> 
> 
> About grub config, the basic stuff in /etc/default/grub is:
> """
> GRUB_TERMINAL="console serial"
> GRUB_SERIAL_COMMAND="serial --speed=9600 --unit=1 --word=8 --parity=no --stop=1"
> GRUB_CMDLINE_XEN="loglvl=all guest_loglvl=all com1=9600,8n1 console=com1,vga"
> """
> 
> nomodeset is not helping.
> 
> Seems like hvc0 contains only serial messages.

Right, that is what you should see on the iLOM.

> Seems also that setting 2 console in linux module would have exclusive access.
> It is important to mention that i can always see grub and Xen logs in both serial and VGA device.
> ttyS0 is not present at all in the dmesg.
> # dmesg |grep tty
> [    0.648440] 00:02: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
> #
> 
> Then i have tried out the following
> # serial OK, no vga after XEN multiboot and earlyprintk
> GRUB_CMDLINE_LINUX="console=hvc0 earlyprintk=xen"
> # serial OK, no vga after XEN multiboot and earlyprintk
> GRUB_CMDLINE_LINUX="console=hvc0 earlyprintk=xen nomodeset"
> # serial OK, no vga after XEN multiboot and earlyprintk
> GRUB_CMDLINE_LINUX="console=hvc0 earlyprintk=xen nomodeset vga=791"
> 
> 
> # VGA OK, no serial after XEN multiboot  and earlyprintk
> GRUB_CMDLINE_LINUX="console=hvc0 console=tty1 earlyprintk=xen"
> 
> 
> # VGA OK, no serial after XEN multiboot  and earlyprintk
> GRUB_CMDLINE_LINUX="console=xvc xencons=xvc console=hvc0 console=tty0 nomodeset earlyprintk=xen"
> 
> # VGA OK, no serial after XEN multiboot  and earlyprintk
> GRUB_CMDLINE_LINUX="xencons=xvc console=xvc0 console=hvc0 console=tty1 earlyprintk=xen nomodeset"
> 
> Really willing to understand how to get the proper output on both serial and VGA.

If you really really want that you can do:

CMD_CMDLINE_LINUX="console=hvc0"

GRUB_CMDLINE_XEN="console=com1,vga vga=text-80x60,keep 	conswitch=ax
console_to_ring"


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