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

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