[Qemu-devel] broken screendump for text mode?

[Qemu-devel] broken screendump for text mode?

[Andriy Gapon]

I use Qemu 0.15.0 (via a FreeBSD qemu-devel-0.15.0 port) and observe the following
problem with the screendump command.

Environment:
- qemu started with a standard vga adapter emulation (not sure if this important)
- SDL interface is used (not sure if this important)
- guest operating system uses the text mode
- monitor console is activated with Ctrl+Alt+2
- screendump command is executed in the monitor console

I observe the following effects in this case:
- contents of the guest screen is "dumped" over the monitoring console
- produced ppm file has only a single top-most line (of characters) from the guest
screen

It seems that the problem is caused in the vga_draw_text function in hw/vga.c.
The problem is that the dpy_update function is called for each line of text and
only the first of such calls produces the ppm output.

Perhaps in the case when full_update is true there should only be a single
dpy_update call for the whole screen.  I think that this should produce a complete
screen dump.  Not sure if that would help with the guest screen contents being
draw over the monitor console.

Thank you.
-- 
Andriy Gapon

Re: [Qemu-devel] broken screendump for text mode?

[Andriy Gapon]

on 30/08/2011 19:50 Andriy Gapon said the following:
> 
> I use Qemu 0.15.0 (via a FreeBSD qemu-devel-0.15.0 port) and observe the following
> problem with the screendump command.
> 
> Environment:
> - qemu started with a standard vga adapter emulation (not sure if this important)
> - SDL interface is used (not sure if this important)
> - guest operating system uses the text mode
> - monitor console is activated with Ctrl+Alt+2
> - screendump command is executed in the monitor console
> 
> I observe the following effects in this case:
> - contents of the guest screen is "dumped" over the monitoring console
> - produced ppm file has only a single top-most line (of characters) from the guest
> screen
> 
> It seems that the problem is caused in the vga_draw_text function in hw/vga.c.
> The problem is that the dpy_update function is called for each line of text and
> only the first of such calls produces the ppm output.
> 
> Perhaps in the case when full_update is true there should only be a single
> dpy_update call for the whole screen.  I think that this should produce a complete
> screen dump.  Not sure if that would help with the guest screen contents being
> draw over the monitor console.

I have to guess that this issue is not of interest to the active qemu developers?
I will try to look into it some time myself, because I find the feature to be
useful from time to time (if it worked).

-- 
Andriy Gapon