Re: [PATCH 0/4] iommu: Prevent oops in iommu_get() and while arch_iommu is in use

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Hi Sakari,

On Sun, Mar 27, 2011 at 8:27 PM, Sakari Ailus
<sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Ramirez Luna, Omar wrote:
>> On Fri, Mar 25, 2011 at 10:13 AM, Sakari Ailus
>> <sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>> Hi,
>>>
>>> This patchset is aimed to fix a problem in arch_iommu implementation
>>> references. When an actual arch_iommu implementation is not loaded while
>>> iommu_get() is being called results to a kernel oops, as well as
>>> removing an arch_iommu implementation which is in use.
>>
>> How about fixing the dependency instead? Right now iommu2 depends on
>> iommu because of the calls to
>> install_iommu_arch/uninstall_iommu_arch... we should change that
>> dependency to iommu depend on iommu2. Something like iommu (plat)
>> querying iommu2 (mach) for devices to install.
>
> There is no direct dependency from a driver using the generic API to a
> particular implementation of the iommu. This comes from the design of
> the iommu framework. The generic layer shouldn't depend on particular
> implementation(s).
>
> What comes to the patch, it works as long as there's only one iommu
> implementation loaded / compiled to the kernel. I wonder if this kind of
> limitation can be accepted.

The generic iommu driver cannot support more than one implementation
loaded at the same time, so your patch is correct by assuming it.

Regards,

David Cohen

>
> Regards,
>
> --
> Sakari Ailus
> sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx
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