Re: [PATCH] powerpc/pseries/iommu: Add TCEs for 16GB pages when RAM is pre-mapped

[Gaurav Batra <gbatra@linux.ibm.com>]

On 5/5/26 11:04 PM, Harsh Prateek Bora wrote:
>
>
> On 06/05/26 2:31 am, Gaurav Batra wrote:
>>
>> On 5/5/26 1:49 PM, Harsh Prateek Bora wrote:
>>>
>>>
>>> On 05/05/26 2:24 am, Gaurav Batra wrote:
>>>> @@ -2431,7 +2437,7 @@ static int iommu_mem_notifier(struct 
>>>> notifier_block *nb, unsigned long action,
>>>>           spin_lock(&dma_win_list_lock);
>>>>           list_for_each_entry(window, &dma_win_list, list) {
>>>>               if (window->direct && (arg->start_pfn << PAGE_SHIFT) <
>>>> -                ddw_memory_hotplug_max()) {
>>>> +                pseries_ddw_max_ram) {
>>>>                   ret |= tce_setrange_multi_pSeriesLP(arg->start_pfn,
>>>>                           arg->nr_pages, window->prop);
>>>
>>> I think not only start_pfn, but end_pfn also needs to be within allowed
>>> range, which may require clamping arg->nr_pages if crossing the limits.
>> The reason to only check for start_pfn is because the range given 
>> will either be in the RAM or pmemory. It can never cross the boundary
>
> Usually as an API, we do not trust the caller, hence the check for
> start_pfn. However, if at all we need to go ahead with that assumption,
> may be document that as a code comment and/or in the commit log also?

I will document it. I am wondering, if instead of capping it to 
start+nrpages,

maybe, return an error. If in the future, we get an error, this needs to be

investigated.

>
>>>
>>>>               }
>>>> @@ -2444,7 +2450,7 @@ static int iommu_mem_notifier(struct 
>>>> notifier_block *nb, unsigned long action,
>>>>           spin_lock(&dma_win_list_lock);
>>>>           list_for_each_entry(window, &dma_win_list, list) {
>>>>               if (window->direct && (arg->start_pfn << PAGE_SHIFT) <
>>>> -                ddw_memory_hotplug_max()) {
>>>> +                pseries_ddw_max_ram) {
>>>>                   ret |= 
>>>> tce_clearrange_multi_pSeriesLP(arg->start_pfn,
>>>>                           arg->nr_pages, window->prop);
>>>>               }
>>>
>