[PATCH] restore export of handle_mm_fault for Mac on Linux

[PATCH] restore export of handle_mm_fault for Mac on Linux

[Gaudenz Steinlin]

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Hi

The kernel modules for Mac on Linux (MOL) need handle_mm_fault. 
MOL is a GPL licensed virtual machine to run MacOS(X) on PPC Linux.

The export for handle_mm_fault was removed with commit
41f9dc5c871600f53c8912b2975971d2a11c1c25. 

Previously the export has been present since handle_mm_fault was
converted from an inline function to a non-inline one. See the thread
starting at http://marc.info/?l=linux-kernel&m=112327941709177&w=2 for
the initial discussion.

With commit 67207b9664a8d603138ef1556141e6d0a102bea7 the export was
moved from arch/ppc/kernel/ppc_ksyms.c to mm/memory.c. In this patch the
explanatory comment /* For MOL */ got lost. Thus to export was not moved
back to it's original place when it was no longer needed for spufs.

The attached patch restores the symbol export (GPL only) in it's
original place. Please consider applying it because this fixes a
regression for MOL.

Thanks

Gaudenz

P.S.: Please CC me and the corresponding Debian bug report on any
replies.

-- 
Ever tried. Ever failed. No matter.
Try again. Fail again. Fail better.
~ Samuel Beckett ~

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diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c
index c6b1aa3..455fb38 100644
--- a/arch/powerpc/kernel/ppc_ksyms.c
+++ b/arch/powerpc/kernel/ppc_ksyms.c
@@ -189,6 +189,7 @@ EXPORT_SYMBOL(set_context);
 extern long mol_trampoline;
 EXPORT_SYMBOL(mol_trampoline); /* For MOL */
 EXPORT_SYMBOL(flush_hash_pages); /* For MOL */
+EXPORT_SYMBOL(handle_mm_fault); /* For MOL */
 #ifdef CONFIG_SMP
 extern int mmu_hash_lock;
 EXPORT_SYMBOL(mmu_hash_lock); /* For MOL */

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Christoph Hellwig]

On Wed, Jun 18, 2008 at 12:14:02PM +0200, Gaudenz Steinlin wrote:
> Hi
> 
> The kernel modules for Mac on Linux (MOL) need handle_mm_fault. 
> MOL is a GPL licensed virtual machine to run MacOS(X) on PPC Linux.

Has been rejected a few times.  An now that we actually have kvm
for powerpc in tree MOL should just merge with that project and
do the right things in tree instead of beeing a really hacky
module subverting the VM.

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Paul Mackerras]

Christoph Hellwig writes:

> On Wed, Jun 18, 2008 at 12:14:02PM +0200, Gaudenz Steinlin wrote:
> > Hi
> > 
> > The kernel modules for Mac on Linux (MOL) need handle_mm_fault. 
> > MOL is a GPL licensed virtual machine to run MacOS(X) on PPC Linux.
> 
> Has been rejected a few times.  An now that we actually have kvm
> for powerpc in tree MOL should just merge with that project and
> do the right things in tree instead of beeing a really hacky
> module subverting the VM.

We don't have KVM for the "classic" 32-bit PowerPC processors, only
for the 44x family.  And doing KVM for the classic 32-bit processors
would probably involve just as much hackery as MOL. :)

Paul.

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Christoph Hellwig]

On Wed, Jun 18, 2008 at 10:45:02PM +1000, Paul Mackerras wrote:
> > Has been rejected a few times.  An now that we actually have kvm
> > for powerpc in tree MOL should just merge with that project and
> > do the right things in tree instead of beeing a really hacky
> > module subverting the VM.
> 
> We don't have KVM for the "classic" 32-bit PowerPC processors, only
> for the 44x family.  And doing KVM for the classic 32-bit processors
> would probably involve just as much hackery as MOL. :)

I don't think so.  Doing it properly in-tree will mean that it is

  a) properly reviewed
  b) means we can do the major VM bits in the kernel without these
     really stupid exports

Have you looked at MOL recently?  It's more than disgusting.

And in addition to these issue we do of course as policy not add
random hooks in the kernel tree for out of tree stuff.  Especially
for hacks like this that don't even have the intention to get merged.

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Gaudenz Steinlin]

On Wed, Jun 18, 2008 at 08:51:31AM -0400, Christoph Hellwig wrote:
> On Wed, Jun 18, 2008 at 10:45:02PM +1000, Paul Mackerras wrote:
> > > Has been rejected a few times.  An now that we actually have kvm
> > > for powerpc in tree MOL should just merge with that project and
> > > do the right things in tree instead of beeing a really hacky
> > > module subverting the VM.
> > 
> > We don't have KVM for the "classic" 32-bit PowerPC processors, only
> > for the 44x family.  And doing KVM for the classic 32-bit processors
> > would probably involve just as much hackery as MOL. :)
> 
> I don't think so.  Doing it properly in-tree will mean that it is
> 
>   a) properly reviewed
>   b) means we can do the major VM bits in the kernel without these
>      really stupid exports
> 
> Have you looked at MOL recently?  It's more than disgusting.
> 
> And in addition to these issue we do of course as policy not add
> random hooks in the kernel tree for out of tree stuff.  Especially
> for hacks like this that don't even have the intention to get merged.

This is not true anymore. See my other message to this thread. Joseph
Jezak is working on a mergeable module.

Gaudenz

-- 
Ever tried. Ever failed. No matter.
Try again. Fail again. Fail better.
~ Samuel Beckett ~

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Alan Cox]

On Wed, 18 Jun 2008 12:14:02 +0200
Gaudenz Steinlin <gaudenz@debian.org> wrote:

> Hi
> 
> The kernel modules for Mac on Linux (MOL) need handle_mm_fault. 
> MOL is a GPL licensed virtual machine to run MacOS(X) on PPC Linux.
> 
> The export for handle_mm_fault was removed with commit
> 41f9dc5c871600f53c8912b2975971d2a11c1c25. 

This sort of thing is going to happen if modules hide out of tree. If MOL
is GPL why isn't it getting submitted to the kernel tree - other
virtualisation subsystems such as KVM are in tree ?

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Gaudenz Steinlin]

On Wed, Jun 18, 2008 at 06:18:56PM +0100, Alan Cox wrote:
> On Wed, 18 Jun 2008 12:14:02 +0200
> Gaudenz Steinlin <gaudenz@debian.org> wrote:
> 
> > Hi
> > 
> > The kernel modules for Mac on Linux (MOL) need handle_mm_fault. 
> > MOL is a GPL licensed virtual machine to run MacOS(X) on PPC Linux.
> > 
> > The export for handle_mm_fault was removed with commit
> > 41f9dc5c871600f53c8912b2975971d2a11c1c25. 
> 
> This sort of thing is going to happen if modules hide out of tree. If MOL
> is GPL why isn't it getting submitted to the kernel tree - other
> virtualisation subsystems such as KVM are in tree ?

There is an effort underway to bring the MOL kernel modules into
a mergeable form. But it's not there yet. Joseph Jezak, the MOl main
developer nowdays is working on it. So MOL no longer want's to hide out
of tree. It just needs some more time.

What I'm asking for is to get the export back, that as far as I can see
was removed accidentialy and that was there before specially for MOL. 

It's true that this has been requested before just after the symbol was
removed and Christoph NAKed it then. But if I remember correctly people
were not aware that this symbol has been exported specifically for MOL
before back then.

Gaudenz

-- 
Ever tried. Ever failed. No matter.
Try again. Fail again. Fail better.
~ Samuel Beckett ~

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Christoph Hellwig]

On Thu, Jun 19, 2008 at 11:58:05AM +0200, Gaudenz Steinlin wrote:
> There is an effort underway to bring the MOL kernel modules into
> a mergeable form. But it's not there yet. Joseph Jezak, the MOl main
> developer nowdays is working on it. So MOL no longer want's to hide out
> of tree. It just needs some more time.

It would be useful if you could send some status-updates to lkml and
the kvm list.

> 
> What I'm asking for is to get the export back, that as far as I can see
> was removed accidentialy and that was there before specially for MOL. 

It was removed intentionally.

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Pekka Enberg]

On Thu, Jun 19, 2008 at 11:58:05AM +0200, Gaudenz Steinlin wrote:
>> There is an effort underway to bring the MOL kernel modules into
>> a mergeable form. But it's not there yet. Joseph Jezak, the MOl main
>> developer nowdays is working on it. So MOL no longer want's to hide out
>> of tree. It just needs some more time.

On Thu, Jun 19, 2008 at 1:38 PM, Christoph Hellwig <hch@infradead.org> wrote:
> It would be useful if you could send some status-updates to lkml and
> the kvm list.

And why not submit MOL to the new linux-staging tree?

Re: [PATCH] restore export of handle_mm_fault for Mac on Linux

[Greg KH]

On Thu, Jun 19, 2008 at 01:46:57PM +0300, Pekka Enberg wrote:
> On Thu, Jun 19, 2008 at 11:58:05AM +0200, Gaudenz Steinlin wrote:
> >> There is an effort underway to bring the MOL kernel modules into
> >> a mergeable form. But it's not there yet. Joseph Jezak, the MOl main
> >> developer nowdays is working on it. So MOL no longer want's to hide out
> >> of tree. It just needs some more time.
> 
> On Thu, Jun 19, 2008 at 1:38 PM, Christoph Hellwig <hch@infradead.org> wrote:
> > It would be useful if you could send some status-updates to lkml and
> > the kvm list.
> 
> And why not submit MOL to the new linux-staging tree?

That sounds good to me, send them over when you have something that
builds and looks semi-sane :)

thanks,

greg k-h