linux-kernel - Re: [PATCH v3 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU

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Date:   Mon, 30 Apr 2018 14:57:58 -0500
From:   Gary R Hook <gary.hook@....com>
To:     "Hook, Gary" <ghook@....com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] iommu/amd: Add basic debugfs infrastructure for
 AMD IOMMU

On 04/17/2018 12:38 PM, Hook, Gary wrote:
> On 4/13/2018 8:08 PM, Mehta, Sohil wrote:
>> On Fri, 2018-04-06 at 08:17 -0500, Gary R Hook wrote:
>>> +
>>> +
>>> +    mutex_lock(&amd_iommu_debugfs_lock);
>>> +    if (!amd_iommu_debugfs) {
>>> +        d_top = iommu_debugfs_setup();
>>> +        if (d_top)
>>> +            amd_iommu_debugfs =
>>> debugfs_create_dir("amd", d_top);
>>> +    }
>>> +    mutex_unlock(&amd_iommu_debugfs_lock);
>>
>>
>> You can do the above only once if you iterate over the IOMMUs here
>>   instead of doing it in amd_iommu_init.
> 
> I'm not sure it matters, given the finite number of IOMMUs in a system, 
> and the fact that this work is done exactly once. However, removal of a 
> lock is fine thing, so I'll move this around.

After thinking about this, and looking at the code, I've decided to 
leave this alone.

v4 is on its way.