linux-kernel - Re: [PATCH 1/1] iommu/amd: Use delayed mmu release notifier

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Date:	Thu, 6 Nov 2014 15:48:51 +0200
From:	Oded Gabbay <oded.gabbay@....com>
To:	Joerg Roedel <joro@...tes.org>
CC:	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] iommu/amd: Use delayed mmu release notifier



On 11/06/2014 03:33 PM, Joerg Roedel wrote:
> On Sat, Oct 18, 2014 at 12:43:27AM +0300, Oded Gabbay wrote:
>> 3. Later, amdkfd's mmu notifier callback (kfd_process_notifier_release()) gets
>>     called and releases more things that are related to the process.
>>     In that function, amd_iommu_unbind_pasid() is explicitly called.
>
> Can't you just register a delayed funtion in
> kfd_process_notifier_release() and call amd_iommu_unbind_pasid() from
> there?
Maybe, I need to think about that. Anyway, I'm still not convinced, please see 
next question.

 >>I really hate to make that part of the IOMMUv2 driver API,
What do you mean ? I don't see I change anything in the API. All the changes are 
internal to amd_iommu_unbind_pasid(). I don't think *anyone* calling to 
amd_iommu_unbind_pasid() will care or will notice the slight change in timing of 
releasing the pasid_state object (instead of immediate release, it is released 
after the iteration on the mmu_notifier list has finished)

> especially since it is going to be turned into a generic IOMMU-API
> extension.
>
> And especially since all these hacks could be avoided if the KFD driver
> would just turn down everything on closing the file descriptor.
>
>
> 	Joerg
>
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