Re: [PATCH] iommu/io-pgtable: Abstract iommu_iotlb_gather access

[Robin Murphy <robin.murphy@arm.com>]

On 2021-08-24 14:55, Geert Uytterhoeven wrote:
> Hi Robin,
> 
> On Fri, Aug 20, 2021 at 3:22 PM Robin Murphy <robin.murphy@arm.com> wrote:
>> Previously io-pgtable merely passed the iommu_iotlb_gather pointer
>> through to helpers, but now it has grown its own direct dereference.
>> This turns out to break the build for !IOMMU_API configs where the
>> structure only has a dummy definition. It will probably also crash
>> drivers who don't use the gather mechanism and simply pass in NULL.
>>
>> Wrap this dereference in a suitable helper which can both be stubbed
>> out for !IOMMU_API and encapsulate a NULL check otherwise.
>>
>> Fixes: 7a7c5badf858 ("iommu: Indicate queued flushes via gather data")
> 
> Is this the right Fixes tag?

Conceptually, yes - that's where the new member was introduced, so 
that's where its accessor should have been introduced as well, had I not 
managed to overlook the structure being conditionally defined and assume 
it didn't need anything special doing. Of course it's not going to make 
much difference in practice since they are immediately adjacent commits 
anyway, but it felt right to point at where I made the fundamental 
mistake rather than where the symptom appeared :)

> The build issue was introduced by:
> Fixes: a8e5f04458c4e496 ("iommu/io-pgtable: Remove non-strict quirk")
> 
>> Reported-by: kernel test robot <lkp@intel.com>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> 
> Thanks, this fixes the build issues I was seeing.
> 
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Thanks for confirming!

Robin.

> 
> Gr{oetje,eeting}s,
> 
>                          Geert
>