Re: [PATCH kernel] powerpc/powernv/ioda2: Add devices only from buses which belong to PE

[Alexey Kardashevskiy]

On 06/13/2015 01:06 AM, Nishanth Aravamudan wrote:
> On 12.06.2015 [16:47:03 +1000], Gavin Shan wrote:
> > On Fri, Jun 12, 2015 at 04:19:17PM +1000, Alexey Kardashevskiy wrote:
> > > The existing code puts all devices from a root PE to the same IOMMU group.
> > > However it is a possible situation when subordinate buses belong to
> > > separate PEs, in this case devices from these subordinate buses
> > > should be added to lower level PE rather to the root PE.
> > >
> > > This limits pnv_ioda_setup_bus_dma() invocation to only PEs which own
> > > all subordinate buses.
> > >
> > > Suggested-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> >
> > Alexey, I think it's good candidate for stable.
>
> Why? This commit message doesn't imply there is a serious bug just a
> "possible" (does that mean theoretical?) situtation and the following:
>
> > > This would be nice to have together with the DDW patchset.
> > > This does not fix anything DDW patchset did, it fixes IOMMU
> > > groups management which is essential for the whole feature to work.
>
> implies it is both related and independent of DDW?


DDW is for fast devices and I just got my hands on a "firestone" machine 
(p8 + nvidia tesla = very fast machine) where this bug appeared first time.


--
Alexey
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