Re: [Xen-devel] Trying fbcon in dom1,but take_over_console fails...

[Mark Hurenkamp <mark.hurenkamp@xxxxxxxxx>]

Hi,

> I suspect you'd be better off getting the xencons to register as ttyS0
> (xencons=ttyS0) so that it doesn't go anywhere near the console, and
> compile in  VT, VT_CONSOLE and DUMMY_CONSOLE.
Tried that, as well as disabling VGA_CONSOLE, but no improvements :-(:-(
however, when built as a module, it is somewhat easier to debug this
problem in fbcon, since dom1 is still running after it segfaults, and I can
still use dmesg to see the printk's (strange that they don't appear on the 
console...).

>
> Please let us know how you get on.

Ok, here's what I found so far:

Using printk statements, I was able to find the culprit, it seems to be the
vc pointer which is not initialised properly.

Here's the piece of code (from fbcon_startup):

        /* Setup default font */
        if (!p->fontdata) {
                if (!fontname[0] || !(font = find_font(fontname)))
                        font = get_default_font(info->var.xres,
                                                info->var.yres);

                DPRINTK("fbcon_startup: ca\n");

                vc->vc_font.width = font->width;
                vc->vc_font.height = font->height;
                vc->vc_font.data = p->fontdata = font->data;
                vc->vc_font.charcount = 256; /* FIXME  Need to support more 
fonts */

                DPRINTK("fbcon_startup: cb\n");

        }

And the oops occurs between the two DPRINTK's...
So I added a check at startup:

static const char *fbcon_startup(void)
{
        const char *display_desc = "frame buffer device";
        struct display *p = &fb_display[fg_console];
        struct vc_data *vc = vc_cons[fg_console].d;
        struct font_desc *font = NULL;
        struct module *owner;
        struct fb_info *info = NULL;
        struct fbcon_ops *ops;
        int rows, cols;
        int irqres;

        DPRINTK("fbcon_startup... fg_console: %d, vc: %d\n",fg_console,vc);

This prints 0 for the fg_console (not necessarely a problem) as well as vc... 
which is defenately a problem since it is dereferenced later!

Seems like the vc_cons is not setup right, I'll have to take a look into vt.c 
I guess.
Could this be due to the missing ps/2 port on domU (since they are assigned to 
dom0)?

Will report back when I know more.


Regards,
Mark.

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