[Qemu-devel] Re: [PATCH] configure: disable opengl per default

[Jan Kiszka]

On 2011-04-09 23:13, Michael Walle wrote:
> There is a bug in nvidia's binary GPU driver, which causes a segmentation
> fault if linked to libGL.
> 
> Signed-off-by: Michael Walle <address@hidden>
> ---
>  configure |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/configure b/configure
> index 2bb3faa..be40a31 100755
> --- a/configure
> +++ b/configure
> @@ -177,6 +177,7 @@ spice=""
>  rbd=""
>  smartcard=""
>  smartcard_nss=""
> +opengl="no"
>  
>  # parse CC options first
>  for opt do

I stumbled over this issue as well, but was unhappy about simply
disabling OpenGL without understanding what goes wrong. Still, I can't
provide a better solution yet, just some maybe helpful insights:

...
00908000-0134f000 rw-p 00000000 00:00 0 [heap]
41944000-43944000 rwxp 00000000 00:00 0
...

That's an extract of /proc/$QEMU_PID/maps with -lGL, and below without it:

00908000-010bd000 rw-p 00000000 00:00 0
010bd000-010be000 rwxp 00000000 00:00 0
010be000-01335000 rw-p 00000000 00:00 0 [heap]
40514000-42514000 rwxp 00000000 00:00 0

IOW, we are lacking the executable code_gen_prologue page. This problem
behaves like a heisenbug, ie. it disappears here when I run qemu in gdb
or under strace. But ftrace confirms that the qemu process issues
mprotect to make the whole heap non-executable after setting up that TCG
buffer - it just doesn't tell me which part of qemu is responsible for this.

Note that I'm still forced to use this wonderful binary nvidia stuff.

Anyone any ideas?
Jan

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