On Thu, Nov 05, 2015 at 11:19:02AM -0500, Lennart Sorensen wrote:
> 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.
I am sure. Xenomai does not use H_DMA on armv7, so, it is not used
if your code, it is not used at all.
>
> 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.
I never said that H_DMA did nothing.
--
Gilles.
https://click-hack.org
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