>> +static void pci_dma_range_setup(struct pci_dev *pdev)
>> +{
>> + struct zpci_dev *zdev = to_zpci(pdev);
>> + struct bus_dma_region *map;
>> +
>> + map = kzalloc(sizeof(*map), GFP_KERNEL);
>> + if (!map)
>> + return;
>> +
>> + map->cpu_start = 0;
>> + map->dma_start = PAGE_ALIGN(zdev->start_dma);
>> + map->size = max(PAGE_ALIGN_DOWN(zdev->end_dma + 1) - map->dma_start, 0);
>
> Ugh, this is my fault as I suggested it, but this max() doesn't work
> here. The zdev->end_dma is unsigned and so is map->dma_start so if the
> former is smaller underflow will occur and the max() won't save us.
> It's largely a theoretical issue since zdev->end_dma + 1 should always
> be larger than zdev->start_dma, but now the max() looks like we thought
> of that, but then it doesn't work.
>
> If we handle it maybe just go with:
>
> aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
> if (aligned_end >= map->dma_start)
> map->size = aligned_end - map->dma_start;
> else
> map->size = 0;
>
Given that it's not really something that's supposed to happen, would it make sense then to add a
WARN_ON_ONCE(map->size == 0);
At the end of this?
