[uml-devel] virtual framebuffer device visible on host

Antoine Martin

author

2006-09-06 20:11 UTC #1 lore raw

Just a thought, but how hard would it be to have a virtual device in the guests that mimics a framebuffer device and is in fact an X window on the host? I think this could almost be a killer-app.
Or is there already a way to do this using VFB?
Surely an X window is rich enough to provide all the primitives that a framebuffer device provides?

Antoine

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Geert Uytterhoeven

2006-09-06 20:31 UTC #2 lore raw

Quoted 6 lines · Antoine Martin

Just a thought, but how hard would it be to have a virtual device in the guests that mimics a framebuffer device and is in fact an X window on the host? I think this could almost be a killer-app.
Or is there already a way to do this using VFB?
Surely an X window is rich enough to provide all the primitives that a framebuffer device provides?

It's been done before (but not yet in mainline), cfr.
http://www.gatago.com/linux/kernel/6105868.html.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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Antoine Martin

author

2006-09-06 22:12 UTC #3 lore raw

Geert,

Thanks for that, the patch is quite small and still applies without too much effort to 2.6.17 (a lot of the rejects are whitespace/no change) Is there any reason not to merge this? Is it hackish or something?

I've only compile tested it here since it seems I can't run any guests kernels since I updated to gcc4.1.1/glibc2.4, but I will certainly revisit this code once mainline is fixed.

As I mentioned yesterday, older kernels die with:
"cannot set up thread-local storage: set_thread_area failed when setting up thread-local storage"
And newer (~ 2.6.16 onwards) fail even quicker on my desktop:

# ./kernel32-2.6.17.11-x11-fb ubd0=./FedoraCore5-x86-root_fs
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...missing
Checking for tmpfs mount on /dev/shm...nothing mounted on /dev/shm
Checking PROT_EXEC mmap in /tmp/...OK
Checking for the skas3 patch in the host:
   - /proc/mm...not found
   - PTRACE_FAULTINFO...not found
   - PTRACE_LDT...not found
UML running in SKAS0 mode
remove_umid_dir - actually_do_remove failed with err = -2

Quoted 13 lines · Geert Uytterhoeven

Quoted 6 lines · Antoine Martin
Just a thought, but how hard would it be to have a virtual device in the guests that mimics a framebuffer device and is in fact an X window on the host? I think this could almost be a killer-app.
Or is there already a way to do this using VFB?
Surely an X window is rich enough to provide all the primitives that a framebuffer device provides?
It's been done before (but not yet in mainline), cfr.
http://www.gatago.com/linux/kernel/6105868.html.
Gr{oetje,eeting}s,

Quoted 9 lines

Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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Jeff Dike

2006-09-15 17:02 UTC #4 lore raw

In reply to Antoine Martin

Quoted 3 lines · Antoine Martin

Just a thought, but how hard would it be to have a virtual device in the guests that mimics a framebuffer device and is in fact an X window on the host? I think this could almost be a killer-app.

There is such a patch in my development tree. The problem is that it totally doesn't work for me, even though it's fine for the guy who wrote it.

It needs to be run on a local X server since it uses the shared memory extension, but even when I do that, I get a black window with nothing in it.

Jeff

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