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

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

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?

>>
>>>               }
>>> @@ -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);
>>>               }
>>