linux-kernel - Re: [PATCH] iommu/amd - Use dev_err to send events to the system log

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Date:   Wed, 14 Feb 2018 09:58:31 -0500
From:   "Hook, Gary" <ghook@....com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Gary R Hook <gary.hook@....com>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/amd - Use dev_err to send events to the system log

On 2/14/2018 6:49 AM, Joerg Roedel wrote:
> On Tue, Feb 13, 2018 at 02:24:56PM -0500, Hook, Gary wrote:
>> Without actually running a driver and getting some debug info, I'll just
>> say that my example compiled, the amd_iommu structure points to a pci_dev
>> which contains a device, and the two possibilities are likely equivalent.
>>
>> I'll vet that, of course, but working under the assumption that they are
>> equivalent, the question becomes, do you have a preference?
> 
> They are not equivalent, your version points to the pci_dev containing
> the IOMMU, my version points to the (virtual) iommu-device for that
> particular iommu in the kernel.
> 
> So the difference in the prefix is:
> 
> 	your version: '0000:00:00.2:'
> 
> 	vs. my version: 'ivhd0:'
> 
> The latter is the better prefix, because it points to the iommu. A
> pci_dev can contain more than one iommu, so that prefix is not specific
> enough. I know that there is currently no hardware implementing multiple
> iommus on one pci_dev, but it is allowed according to the spec.

Excellent; specificity is good. I'll crank a new version using that
device.

Thank you!