[Xenomai] Any idea how to fix ipipe failing to compile with ARM LPAE enabled?

Lennart Sorensen lsorense at csclub.uwaterloo.ca
Mon Aug 25 04:27:58 CEST 2014

On Fri, Aug 22, 2014 at 11:36:33PM +0200, Gilles Chanteperdrix wrote:
> On 08/22/2014 11:31 PM, Lennart Sorensen wrote:
> > Any idea how to fix ipipe to not cause a linking error when LPAE is enabled on arm?
> > 
> > I see the function __ipipe_pin_range_globally is inside an ifdef block that says essentially:
> > 
> > #if !IPIPE
> > define __ipipe_pin_range_globally as do nothing
> > #else
> > #if !LPAE
> > define __ipipe_pin_range_globally function
> > #endif
> > #endif
> > 
> > So if IPIPE and LPAE are both true, then the function is never defined.
> > 
> > This is in arch/arm/mm/fault.c
> > 
> I do not believe this is intentional. That being said, the Linux code in
> the #ifdef is not reassuring: exception handlers are not registered when
> the kernel is compiled with LPAE, which could mean that exceptions are
> used for LPAE when compiled with LPAE. If this is the case, then LPAE
> should not be enabled, otherwise your applications will not stay in
> primary mode when these faults happen. How much RAM do you have, can you
> really test LPAE ?

LPAE is required on arm to enable KVM, which we want to experiment with.
Don't need it for the ram quantity.

Len Sorensen

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