RE: Minimal requirements to run L4linux using only a serial console - l4-hackers

29 Aug 2014


      Hi Martin,
That was a very useful tip. I simply changed the default value in kernel/fiasco/src/kern/config.cpp from SERIAL_ESC_IRQ to SERIAL_ESC_NOIRQ which leads to polling (I am guessing) and voila! It works! I even tried on the actual SCC and it works! I can break into the debugger as well as input to l4linux.
Thanks a lot for your help for your help.
Best,
Ramya
________________________________________
From: Masti  Ramya Jayaram
Sent: 29 August 2014 17:48
To: Martin Schröder; l4-hackers@os.inf.tu-dresden.de
Subject: RE: Minimal requirements to run L4linux using only a serial console
Also with acpi on, it does enter the debugger in qemu.
Best,
Ramya
________________________________________
From: Masti  Ramya Jayaram
Sent: 29 August 2014 17:45
To: Martin Schröder; l4-hackers@os.inf.tu-dresden.de
Subject: RE: Minimal requirements to run L4linux using only a serial console
Hey Martin,
No I just realized that ESC does not break into the debugger. But I can clearly see that the process instead of printing "Hello world" prints "ello World" :)
What could the reason be?
Thanks,
Ramya
________________________________________
From: l4-hackers [l4-hackers-bounces@os.inf.tu-dresden.de] on behalf of Martin Schröder [martin.schroeder@openlimit.com]
Sent: 29 August 2014 17:35
To: l4-hackers@os.inf.tu-dresden.de
Subject: Re: Minimal requirements to run L4linux using only a serial console
Hi Ramya,
a: No, its not a must. The UART could also be polled (by a timer) to see if something arrived.
b: At least regarding l4linux there is nothing more to it - afaik.
But let's go back to the hello word example on the SCC. What happens if you press the <ESC> key? Does it break into the JDB debugger?
Best regards,
    Martin
Am 29.08.2014 um 16:56 schrieb Masti Ramya Jayaram:
...
Hey Martin,
I am trying to run l4linux/fiasco on the Intel SCC which does have a pic-8259. The Intel SCC does not have a BIOS and does not have any ACPI tables which I think qemu generates on the fly.  It also does not use a Screen or keyboard.
I obtained a patch from Markus Partheymueller which they used to boot fiasco on the SCC. With it I am able to run hello world both in qemu with no-acpi as well as on the SCC successfully.
The patch to the best of my knowledge does the following:
a. Makes the cmdline also parse an argument so that the frequency is an input (533Mhz)
b. Uses the apic timer for scheduling.
c. Disables the pic-8259 because it does not exist. Instead the core in the SCC has two interrupt lines and this patch initializes these lines as interrupts to the core.
d. Disables keyboard and screen and enables a serial line for communication instead
e. Disables super pages because the SCC does not support it.
So, when I try the patched  fiasco/L4linux on qemu, it works when I do not disable acpi. But since the SCC does not have any ACPI/IO-APIC, when I try to run the same thing on qemu with ACPI off, l4linux boots but is not responsive to input.
In short:
when I run with I (below) , my l4linux responds to input and with II (below) not.
qemu-system-i386 -m 256 -serial stdio -kernel bootstrap_l4linux.elf -append "-arg=fiasco,,-serial_esc -freq=533000"
qemu-system-i386 -no-acpi -m 256 -serial stdio -kernel bootstrap_l4linux.elf -append "-arg=fiasco,,-serial_esc -freq=533000"
Now the question is:
a. Is the IO-APIC a must for the serial line?
b. Are ACPI tables just a matter of writing data at the right memory locations (e..g, qemu lets you give the acpi-table as input I noticed)?  Or is there more to it?
Thanks for your patience,
ramya

From: l4-hackers [l4-hackers-bounces@os.inf.tu-dresden.de] on behalf of Martin Schröder [martin.schroeder@openlimit.com]
Sent: 29 August 2014 16:29
To: l4-hackers@os.inf.tu-dresden.de
Subject: Re: Minimal requirements to run L4linux using only a serial console
Hi Ramya,
Why did you disable the PIC?
What is your aim with ACPI and why should this lead to a change in the UART driver?
And what has the serial console to do with ACPI tables?
For me the topics have at the moment very little in common or I am missing something.
Best regards,
     Martin
Am 29.08.2014 um 15:58 schrieb Masti Ramya Jayaram:
...
Also, given that the thing works with ACPI on, wouldn't it be better to include ACPI information in the boot instead of changing the driver? Or is this impossible?
Best,
Ramya

From: Masti  Ramya Jayaram
Sent: 29 August 2014 15:55
To: Martin Schröder; l4-hackers@os.inf.tu-dresden.de
Subject: RE: Minimal requirements to run L4linux using only a serial console
Hey Martin,
Back on the list ;-)
Ok, I can confirm that when I busy loop during fiasco init, I can actually see the character that I typed. So would I have to change the l4ser driver in Linux or the main driver in under pkg/l4/bootstrap or under fiasco in vkey.cpp? :)
Thanks,
ramya
________________________________________
From: Masti  Ramya Jayaram
Sent: 29 August 2014 12:15
To: Martin Schröder; l4-hackers@os.inf.tu-dresden.de
Subject: RE: Minimal requirements to run L4linux using only a serial console
Hey Martin,
I cleaned up my build and it worked - the mistake was mine. I had a question regarding ACPI. The target machine I am using has no BIOS/ACPi support. So, when I boot linux on it my console input does not work.This is similar to booting in qemu with the -no-acpi option. Serial console output works (I can see the prompt of L4Linux) but input does not.
Is there something special to do when booting with a serial console but no ACPI tables?
Thanks,
ramya
________________________________________
From: Martin Schröder [martin.schroeder@openlimit.com]
Sent: 27 August 2014 18:32
To: Masti  Ramya Jayaram; l4-hackers@os.inf.tu-dresden.de
Subject: Re: Minimal requirements to run L4linux using only a serial console
Hi Masti,
you have  all of them already! I did not alter any other file beside the files you already sent. I inserted them into a fresh
snapshot (http://l4re.org/download/snapshots-oc/l4re-snapshot-2014053111.tar.xz) and started building. Since "drops-rd.rd" was not
found in the snapshot, I just renamed "ramdisk-x86.rd" to "drops-rd.rd". Nothing more.
Martin
Am 27.08.2014 um 18:02 schrieb Masti Ramya Jayaram:
...
Hey Martin,
thanks for the quick response. Could you send me your configs (l4linux, fiasco, l4re) so that I can try it with that?
Thanks,
Ramya
________________________________________
From: l4-hackers [l4-hackers-bounces@os.inf.tu-dresden.de] on behalf of Martin Schröder [martin.schroeder@openlimit.com]
Sent: 27 August 2014 16:28
To: l4-hackers@os.inf.tu-dresden.de
Subject: Re: Minimal requirements to run L4linux using only a serial console
Hi Masti,
I just applied your config, replaced "drops-rd.rd" by "ramdisk-x86.rd" and everything (command prompt, debugger) runs fine as
expected in Qemu. Maybe you ran into a similar problem as described in this thread:
http://os.inf.tu-dresden.de/pipermail/l4-hackers/2012/thread.html#5165
Best regards,
       Martin
Am 27.08.2014 um 15:18 schrieb Masti Ramya Jayaram:
...
Sorry, a couple of typos in the l4linux.cfg
--vim:set ft=lua:
L4.default_loader:start({ caps = {
          log = L4.Env.log:m("rws"),
        },
        l4re_dbg = L4.Dbg.Warn,
        log = { "l4linux", "yellow" },
      }, "rom/vmlinuz mem=64M console=ttyLv0 l4x_rd=rom/drops-rd.rd root=1:0 ramdisk_size=4000 l4ser.vkey_enable=1");
Thanks in advance,
ramya

From: l4-hackers [l4-hackers-bounces@os.inf.tu-dresden.de] on behalf of Masti  Ramya Jayaram [rmasti@inf.ethz.ch]
Sent: 27 August 2014 14:07
To: l4-hackers@os.inf.tu-dresden.de
Subject: Minimal requirements to run L4linux using only a serial console
Dear all,
I am trying to run L4linux on fiasco/l4re but with the keyboard and VGA disabled. I can get all the way to the command prompt (of the shell) in the initramfs but then, on pressing a key, I get a page fault and I cannot debug the system anymore using the serial_esc. I suspect it is my configuration which I have provided below. I was wondering what the minimal packages are to achieve this.
modules.list:
entry l4linux
kernel fiasco -serial_esc -freq=533000
roottask moe rom/l4linux.cfg
module l4re
module ned
module l4linux.cfg
module io
module vmlinuz
module drops-rd.rd
I have disabled the framebuffer and input server in the L4linux stub drivers configuration and enabled the serial console.
l4linux.cfg:
--vim:set ft=lua:
L4.default_loader:start({ caps = {
          log = L4.Env.log:m("rws"),
        },
        l4re_dbg = L4.Dbg.Warn,
        log = { "l4linux", "yellow" },
      }, "rom/io -vvvv rom/vmlinuz mem=64M console=ttyLv0 l4x_rd=rom/drops-rd.rd root=1:0 ramdisk$
I also specify a custom frequency for my board to fiasco.oc, do I have to make similar modifications to l4linux (e.g., Timer frequency)?
Thanks,
Ramya
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