Re: [PATCH v2 2/6] powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows

[Alexey Kardashevskiy]

On 02/07/2020 00:04, Leonardo Bras wrote:
> On Wed, 2020-07-01 at 18:17 +1000, Alexey Kardashevskiy wrote:
>>
>>> +#define DDW_EXT_SIZE		0
>>> +#define DDW_EXT_RESET_DMA_WIN	1
>>> +#define DDW_EXT_QUERY_OUT_SIZE	2
>>
>> #define DDW_EXT_LAST (DDW_EXT_QUERY_OUT_SIZE + 1)
>> ...
>>
>>
>>> +
>>>  static struct iommu_table_group *iommu_pseries_alloc_group(int node)
>>>  {
>>>  	struct iommu_table_group *table_group;
>>> @@ -339,7 +343,7 @@ struct direct_window {
>>>  /* Dynamic DMA Window support */
>>>  struct ddw_query_response {
>>>  	u32 windows_available;
>>> -	u32 largest_available_block;
>>> +	u64 largest_available_block;
>>>  	u32 page_size;
>>>  	u32 migration_capable;
>>>  };
>>> @@ -875,13 +879,29 @@ static int find_existing_ddw_windows(void)
>>>  machine_arch_initcall(pseries, find_existing_ddw_windows);
>>>  
>>>  static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
>>> -			struct ddw_query_response *query)
>>> +		     struct ddw_query_response *query,
>>> +		     struct device_node *parent)
>>>  {
>>>  	struct device_node *dn;
>>>  	struct pci_dn *pdn;
>>> -	u32 cfg_addr;
>>> +	u32 cfg_addr, query_out[5], ddw_ext[DDW_EXT_QUERY_OUT_SIZE + 1];
>>
>> ... and use DDW_EXT_LAST here.
> 
> Because of the growing nature of ddw-extensions, I intentionally let
> this be (DDW_EXT_QUERY_OUT_SIZE + 1). If we create a DDW_EXT_LAST, it
> will be incremented in the future if more extensions come to exist.
> 
> I mean, I previously saw no reason for allocating space for extensions
> after the desired one, as they won't be used here.

Ah, my bad, you're right.


> 
>>
>>
>>>  	u64 buid;
>>> -	int ret;
>>> +	int ret, out_sz;
>>> +
>>> +	/*
>>> +	 * From LoPAR level 2.8, "ibm,ddw-extensions" index 3 can rule how many
>>> +	 * output parameters ibm,query-pe-dma-windows will have, ranging from
>>> +	 * 5 to 6.
>>> +	 */
>>> +
>>> +	ret = of_property_read_u32_array(parent, "ibm,ddw-extensions",
>>> +					 &ddw_ext[0],
>>> +					 DDW_EXT_QUERY_OUT_SIZE + 1);
> 
> In this case, I made sure not to cross (DDW_EXT_QUERY_OUT_SIZE + 1)
> while reading the extensions from the property.
> 
> What do you think about it? 

I think you want something like:

static inline int ddw_read_ext(const struct device_node *np, int extnum,
u32 *ret)
{
retun of_property_read_u32_index(np, "ibm,ddw-extensions", extnum + 1, ret);
}

These "+1"'s all over the place are confusing.


-- 
Alexey