On Thu, Nov 05, 2015 at 04:55:49PM +0100, Gilles Chanteperdrix wrote:
> As I said, that depends on the contents of the /proc file described
> in Documentation/arm/mem_alignment
> 
> If that file is configured to fixup faults in kernel, then every
> alignment fault in user-space triggers a trap, the trap handler
> simulates the faulting instruction and returns to user-space. If you
> do that from a Xenomai task running in primary mode, it should cause
> the task to switch to secondary mode, unless there is a bug in the
> I-pipe patch regarding that particular issue (like a fault not
> transmitted to Xenomai).

Well I tried changing that setting to 0 (ignore) and that just crashed
the system instead.

> Xenomai does not change the type of the RAM memory, the H_DMA flag
> only has an effect on heaps created with Xenomai shared user/kernel
> heaps interface. Xenomai only use that flag automatically on arm
> machines with VIVT cache. armv7 do not have VIVT cache as far as I
> know.

Hmm, not sure.

It does appear that when LPAE is enabled H_DMA does do something on arm,
but only when LPAE is enabled since that enables ZONE_DMA.

-- 
Len Sorensen

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