Re: [Xen-devel] [PATCH] enable/disable dom0_11_mapping from command-line and default to enabled

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-01-06 at 11:12 +0000, Stefano Stabellini wrote:
> On Sun, 5 Jan 2014, Julien Grall wrote:
> > On 01/05/2014 07:24 PM, Stefano Stabellini wrote:
> > > On Sun, 5 Jan 2014, Karim Raslan wrote:
> > > > Signed-off-by: Karim Raslan <karim.allah.ahmed@xxxxxxxxx>
> > > 
> > > Thanks!
> > > Given that dom0_11_mapping is an int, the patch is OK.
> > > However it might be better to turn dom0_11_mapping into a bool_t and use
> > > boolean_param instead.
> > 
> > After reading the thread "Master not working on AllWinner A20", I still 
> > don't
> > see why this patch is useful.
> > 
> > Unless if the platform has an IOMMU, the 1:1 mapping for the memory SHOULD 
> > be
> > enabled. Otherwise DMA-capable won't work.
> > 
> > See my answer on your mail (thread "Master not working on AllWinner for 
> > A20")
> > for a proper fix.
> 
> It is only useful for debugging and development. It should not be used
> in production.

Assuming we are talking about the dom0_11_mapping command line parameter
then for debugging and development the constant in the code can simply
be changed, then there is no danger of an end user thinking it can be
useful.

That's essentially why I dropped the option from my initial series which
added the dom0_11_mapping variable.

Ian.



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