Re: [Xen-devel] [PATCH]: vm86 and xen kernels

[Juan Quintela <quintela@xxxxxxxxxx>]

On Wed, 2006-03-08 at 10:42 +0000, Keir Fraser wrote:
> On 7 Mar 2006, at 20:19, Juan Quintela wrote:
> 
> >     vm86() call don't work at all on xen kernels, and it didn't worked
> > either with kernels previous to the TSS removal.  VM86 requires TSS
> > support, then it is better to disable it.  Specially because it didn't
> > work.  This patch disables it for xen kernels.
> >
> > Patch didn't apply because init/Kconfig don't exist on the sparse tree.
> >
> > (And no, I don't know either why an x86 option is on that file :)
> 
> We test vm86 support in our regression tests, so it does seem to be 
> working.

After further investigation, it shows that _sometimes_ it works. Problem
is the definition of "sometimes".  In any FC5 system, when kudzu tries
to execute bios at 0xc00000 with vm86, kudzu dies with a segmentation
fault.

It fails with xen-unstable kernels, i.e. it is not related to any fedora
kernel patch, with xen-unstable configuration :(
It happens the same with yesterday xen-unstable kernels, but I don't
have unmodified kernels installed just now.  This kudzu version has been
modified to print the arguments that are passed to vm86.

quintela$ uname -a
Linux gnomo.mitica 2.6.16-rc3-xen0 #1 Tue Mar 7 12:09:03 CET 2006 i686
athlon i386 GNU/Linux
quintela$ ~/work/kudzu-1.2.33/kudzu

ERROR - You must be root to run kudzu.
quintela$ sudo ~/work/kudzu-1.2.33/kudzu
ebx: 0
0
0
0
0
0
4f00
0
0
0
0


sudo strace ~/work/kudzu-1.2.33/kudzu

<lots of output removed>

write(1, "gs: 0 gsh:0\n", 12gs: 0 gsh:0
)           = 12
vm86old(0x806f82c <unfinished ...>
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
Process 3518 detached

This is completelly reproducible, and has happened I think that always.

Later, Juan.


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