Re: [Xci-devel] qemu-dm segfault at pv guest system

[Jean Guyader <jean.guyader@xxxxxxxxx>]

Hi,

2009/9/1 Kornelius Prell <kornelius.prell@xxxxxxxxxxxxxx>:
> Hello,
>
> I set the vnc option in a pv domain config file (Ubuntu 9.04 32 bit with XCI
> kernel/initrd) to test qemu-dm and its framebuffer support (see below for
> full config file).
> Unfortunately it runs into a segmentation fault as soon as I try to access
> it via a vnc viewer (dom0 dmesg):
> [  156.326275] qemu-dm[1500]: segfault at 494 ip 080c2f7a sp bff11b40 error
> 4 in qemu-dm[8048000+10d000]
>
> Debugging with gdb shows the cause of the error in the function xenfb_update
> in /xenclient-ioemu/hw/xenfb.c
> The parameter passed to the function is 0, but as it should be a pointer to
> the xenfb device it results later in a segmentation fault (as the height and
> the width of it are tested to be not 0).
>
> Hower using xenconsole to connect to the domain reveals that xenbus tries to
> connect to the vfb device during the boot process, but fails (domU console):
> [    5.678469] XENBUS: Waiting for devices to initialise:
> 295s...290s...285s...(...)...0s...
> [  300.588592] XENBUS: Timeout connecting to device: device/vfb/0 (local
> state 3, remote state 1)
>

That is because the devices are not properly initialise. Vincent an idea?

> Looking at /proc/fb however shows its existence:
> cat /proc/fb
> 0 VGA16 VGA
> 1 xen
>
> pv dom config file:
> uuid = 01000000-0000-0000-0000-102130000004
> hvm = false
> memory = 1024
> debug = true
> kernel = /boot/vmlinuz-xci
> initrd = /boot/initrd.img-xci
> cmdline = root=/dev/sda1 video=xenfb

That should be cmdline = root=/dev/xvda1

> disk = /dev/sda:file:sda:w:disk

I don't know what you are trying to do.
Pvm guest only boots from partition not from disk.

disk = <path of a file>:file:xvda1:w:disk
disk = <path of a disk>:phy:xvda1:w:disk

> vif = bridge=xenbr0
> serial = /dev/tty2
> extra-hvm = dom0-input=1
This is to use dom0 keyboard and mouse directly so you don

> extra-hvm = intel=

You don't want to have this option here. This is only to have the
output of your vm on the top of an already initialize (it means
initialize by another domain) intel graphic card.

> extra-hvm = std-vga=

For pv guest you use xenfb so you probably don't need that as well.

>
> Am I missing essential parameters?
>

There is a new xenvm option now call display.
So you should probably use in you config file,
but we need to wait for Vincent confirmation on that one.

display = vnc

Thanks,
Jean

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