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

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Message-ID: <557B0D3C.6040100@ozlabs.ru>
Date:	Sat, 13 Jun 2015 02:47:56 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH kernel] powerpc/powernv/ioda2: Add devices only from buses
 which belong to PE

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@...ux.vnet.ibm.com>
>>> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
>>
>> 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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