[PATCH v2 13/14] powerpc/pseries/iommu: Make use of DDW for indirect mapping

[Alexey Kardashevskiy]

On 13/04/2021 17:33, Leonardo Bras wrote:
> On Tue, 2021-04-13 at 17:18 +1000, Alexey Kardashevskiy wrote:
>>
>> On 13/04/2021 15:49, Leonardo Bras wrote:
>>> Thanks for the feedback!
>>>
>>> On Tue, 2020-09-29 at 13:56 +1000, Alexey Kardashevskiy wrote:
>>>>> -static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)
>>>>> +static phys_addr_t ddw_memory_hotplug_max(void)
>>>>
>>>>
>>>> Please, forward declaration or a separate patch; this creates
>>>> unnecessary noise to the actual change.
>>>>
>>>
>>> Sure, done!
>>>
>>>>
>>>>> +		_iommu_table_setparms(tbl, pci->phb->bus->number, create.liobn, win_addr,
>>>>> +				      1UL << len, page_shift, 0, &iommu_table_lpar_multi_ops);
>>>>> +		iommu_init_table(tbl, pci->phb->node, 0, 0);
>>>>
>>>>
>>>> It is 0,0 only if win_addr>0 which is not the QEMU case.
>>>>
>>>
>>> Oh, ok.
>>> I previously though it was ok to use 0,0 here as any other usage in
>>> this file was also 0,0.
>>>
>>> What should I use to get the correct parameters? Use the previous tbl
>>> it_reserved_start and tbl->it_reserved_end is enough?
>>
>> depends on whether you carry reserved start/end even if they are outside
>> of the dma window.
>>
> 
> Oh, that makes sense.
> On a previous patch (5/14 IIRC), I changed the behavior to only store
> the valid range on tbl, but now I understand why it's important to
> store the raw value.
> 
> Ok, I will change it back so the reserved range stays in tbl even if it
> does not intersect with the DMA window. This way I can reuse the values
> in case of indirect mapping with DDW.
> 
> Is that ok? Are the reserved values are supposed to stay the same after
> changing from Default DMA window to DDW?

I added them to know what bits in it_map to ignore when checking if 
there is any active user of the table. If you have non zero reserved 
start/end but they do not affect it_map, then it is rather weird way to 
carry reserved start/end from DDW to no-DDW. May be do not set these at 
all for DDW with window start at 1<<59 and when going back to no-DDW (or 
if DDW starts at 0) - just set them from MMIO32, just as they are 
initialized in the first place.



-- 
Alexey