linux-kernel - Re: [PATCH 2/2] powerpc/iommu: check dev->iommu_group before remove a device from iommu

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Message-ID: <5215BC76.10105@ozlabs.ru>
Date:	Thu, 22 Aug 2013 17:23:34 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	Wei Yang <weiyang@...ux.vnet.ibm.com>
CC:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	benh@....ibm.com, paulus@....ibm.com
Subject: Re: [PATCH 2/2] powerpc/iommu: check dev->iommu_group before remove
 a device from iommu_group

On 08/19/2013 11:55 AM, Wei Yang wrote:
> On Mon, Aug 19, 2013 at 11:39:49AM +1000, Alexey Kardashevskiy wrote:
>> On 08/19/2013 11:29 AM, Wei Yang wrote:
>>> On Fri, Aug 16, 2013 at 08:15:36PM +1000, Alexey Kardashevskiy wrote:
>>>> On 08/16/2013 08:08 PM, Wei Yang wrote:
>>>>> ---
>>>>>  arch/powerpc/kernel/iommu.c |    3 ++-
>>>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>>>>
>>>>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
>>>>> index b20ff17..5abf7c3 100644
>>>>> --- a/arch/powerpc/kernel/iommu.c
>>>>> +++ b/arch/powerpc/kernel/iommu.c
>>>>> @@ -1149,7 +1149,8 @@ static int iommu_bus_notifier(struct notifier_block *nb,
>>>>>  	case BUS_NOTIFY_ADD_DEVICE:
>>>>>  		return iommu_add_device(dev);
>>>>>  	case BUS_NOTIFY_DEL_DEVICE:
>>>>> -		iommu_del_device(dev);
>>>>> +		if (dev->iommu_group)
>>>>> +			iommu_del_device(dev);
>>>>>  		return 0;
>>>>>  	default:
>>>>>  		return 0;
>>>>>
>>>>
>>>> This one seems redundant, no?
>>>
>>> Sorry for the late.
>>>
>>> Yes, these two patches have the same purpose to guard the system, while in two
>>> different places.  One is in powernv platform, the other is in the generic iommu 
>>> driver.
>>>
>>> The one in powernv platform is used to correct the original logic.
>>>
>>> The one in generic iommu driver is to keep system safe in case other platform to
>>> call iommu_group_remove_device() without the check.
>>
>>
>> But I am moving bus notifier to powernv code (posted a patch last week,
>> otherwise Freescale's IOMMU conflicted) so this won't be the case.
> 
> Yes, I see the patch.
> 
> This means other platforms, besides powernv, will check the dev->iommu_group
> before remove the device? This would be a convention?
> 
> If this is the case, the second patch is enough. We don't need to check it in
> generic iommu driver.
> 
> Since I am not very familiar with the code convention, I post these two
> patches together. This doesn't mean I need to push both of them. Your comments
> are welcome, lets me understand which one is more suitable in this case.


Ok. So. I included the check in the bus notifier which I moved to powernv
platform, I guess I'll repost the series soon.

Good luck with pushing the fix for drivers/iommu/iommu.c :)



-- 
Alexey
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