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Date:	Mon, 22 Dec 2014 12:22:18 +0200
From:	Oded Gabbay <oded.gabbay@....com>
To:	Christian König <deathsimple@...afone.de>,
	"Dave Airlie" <airlied@...il.com>
CC:	"Deucher, Alexander" <Alexander.Deucher@....com>,
	"Elifaz, Dana" <Dana.Elifaz@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/3] amdkfd: Don't clear *kfd2kgd on kfd_module_init



On 12/22/2014 11:26 AM, Oded Gabbay wrote:
>
>
> On 12/22/2014 10:57 AM, Christian König wrote:
>> Am 22.12.2014 um 08:43 schrieb Oded Gabbay:
>>>
>>>
>>> On 12/22/2014 09:40 AM, Dave Airlie wrote:
>>>>>>>>> There should be, but when the modules are compiled in, they are loaded
>>>>>>>>> based on
>>>>>>>>> link order only, if they are in the same group, and the groups are
>>>>>>>>> loaded by a
>>>>>>>>> pre-defined order.
>>>>>>>>
>>>>>>>> Is that really still up to date? I've seen effort to change that
>>>>>>>> something like
>>>>>>>> 10+ years ago when Rusty reworked the module system. And it is comming
>>>>>>>> up on the
>>>>>>>> lists again from time to time.
>>>>>>>
>>>>>>>  From what I can see in the Makefile rules, code and google, yes, that's
>>>>>>> still
>>>>>>> the situation. If someone will prove me wrong I will be more than happy
>>>>>>> to
>>>>>>> correct my code.
>>>>>>>>
>>>>>>>>
>>>>>>>>> I don't want to move iommu before gpu, so I don't have a solution for
>>>>>>>>> the
>>>>>>>>> order between amdkfd and amd_iommu_v2.
>>>>>>>>
>>>>>>>> Why not? That's still better than creating a kernel workqueue,
>>>>>>>> scheduling one
>>>>>>>> work item on it, rescheduling the task until everything is completed and
>>>>>>>> you can
>>>>>>>> continue.
>>>>>>>
>>>>>>> Because I don't know the consequences of moving an entire subsystem in
>>>>>>> front
>>>>>>> of another one. In addition, even if everyone agrees, I'm pretty sure
>>>>>>> that
>>>>>>> Linus won't be happy to do that in -rc stages. So maybe this is something
>>>>>>> to
>>>>>>> consider for 3.20 merge window, but I would still like to provide a
>>>>>>> solution
>>>>>>> for 3.19.
>>>>>>
>>>>>>
>>>>>> Yeah, true indeed. How about depending on everything being compiled as
>>>>>> module
>>>>>> for 3.19 then? Still better than having such a hack in the driver for as a
>>>>>> temporary workaround for one release.
>>>>>>
>>>>> I thought about it, but because this problem was originally reported by a
>>>>> user that told us he couldn't use modules because of his setup, I decided
>>>>> not to.
>>>>> I assume there are other users out there who needs this option (compiled
>>>>> everything in the kernel - embedded ?), so I don't want to make their life
>>>>> harder.
>>>>>
>>>>> In addition, saying it is a workaround for one release is true in case
>>>>> moving iommu subsystem in front of gpu subsystem is acceptable and doesn't
>>>>> cause other problems, unknown at this point.
>>>>>
>>>>> Bottom line, my personal preference is to help the users _now_ and if a
>>>>> better fix is found in the future, change the code accordingly.
>>>>
>>>> My guess is moving the iommu subsystem in front of the GPU would be rational.
>>>>
>>>> It does seem like it would generally have a depend in that order.
>>>>
>>>> Dave.
>>>>
>>> Dave,
>>> I agree, but don't you think it is too risky for -rc stages ?
>>> If not, I can try it and if it works on KV, I can submit a patch.
>>> But if you do think it is risky, what do you recommend for 3.19 ? Do the fix I
>>> suggested or disable build-in compilation option ?
>>
>> I would say create the patch of changing the order (should be trivial), describe
>> in detail in the commit message what this is supposed to fix and why such an
>> severe change was done in -rc1 and submit it upstream.
>>
>> We can still revert it in -rc2 if it breaks anything.
>>
>> Christian.
>>
>>>
>>>     Oded
>>
>
> OK, I'll try it on my machine and if it works, I will send the patch to the list.
>
>      Oded
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

So I checked it and all my HSA tests are passing on KV machine.
I will send the patches today. Please discard the current patch-set.

	Oded
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