[dpdk-stable] [PATCH v3 1/6] mem: add function for checking memsegs IOVAs addresses

[Burakov, Anatoly]

On 10-Jul-18 12:14 PM, Eelco Chaudron wrote:
> 
> 
> On 10 Jul 2018, at 12:52, Alejandro Lucero wrote:
> 
>> On Tue, Jul 10, 2018 at 11:06 AM, Eelco Chaudron <echaudro at redhat.com>
>> wrote:
>>
>>>
>>>
>>> On 10 Jul 2018, at 11:34, Alejandro Lucero wrote:
>>>
>>> On Tue, Jul 10, 2018 at 9:56 AM, Eelco Chaudron <echaudro at redhat.com>
>>>> wrote:
>>>>
>>>>
>>>>>
>>>>> On 4 Jul 2018, at 14:53, Alejandro Lucero wrote:
>>>>>
>>>>> A device can suffer addressing limitations. This functions checks
>>>>>
>>>>>> memsegs have iovas within the supported range based on dma mask.
>>>>>>
>>>>>> PMD should use this during initialization if supported devices
>>>>>> suffer addressing limitations, returning an error if this function
>>>>>> returns memsegs out of range.
>>>>>>
>>>>>> Another potential usage is for emulated IOMMU hardware with 
>>>>>> addressing
>>>>>> limitations.
>>>>>>
>>>>>> Signed-off-by: Alejandro Lucero <alejandro.lucero at netronome.com>
>>>>>> Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>
>>>>>> ---
>>>>>>  lib/librte_eal/common/eal_common_memory.c  | 33
>>>>>> ++++++++++++++++++++++++++++++
>>>>>>  lib/librte_eal/common/include/rte_memory.h |  3 +++
>>>>>>  lib/librte_eal/rte_eal_version.map         |  1 +
>>>>>>  3 files changed, 37 insertions(+)
>>>>>>
>>>>>> diff --git a/lib/librte_eal/common/eal_common_memory.c
>>>>>> b/lib/librte_eal/common/eal_common_memory.c
>>>>>> index fc6c44d..f5efebe 100644
>>>>>> --- a/lib/librte_eal/common/eal_common_memory.c
>>>>>> +++ b/lib/librte_eal/common/eal_common_memory.c
>>>>>> @@ -109,6 +109,39 @@
>>>>>>         }
>>>>>>  }
>>>>>>
>>>>>> +/* check memseg iovas are within the required range based on dma 
>>>>>> mask
>>>>>> */
>>>>>> +int
>>>>>> +rte_eal_check_dma_mask(uint8_t maskbits)
>>>>>> +{
>>>>>> +
>>>>>> +       const struct rte_mem_config *mcfg;
>>>>>> +       uint64_t mask;
>>>>>> +       int i;
>>>>>> +
>>>>>>
>>>>>>
>>>>> I think we should add some sanity check to the input maskbits, i.e.
>>>>> [64,0)
>>>>> or [64, 32]? What would be a reasonable lower bound.
>>>>>
>>>>>
>>>>> This is not a user's API, so any invocation will be reviewed, but I 
>>>>> guess
>>>> adding a sanity check here does not harm.
>>>>
>>>> Not sure about lower bound but upper should 64, although it does not 
>>>> make
>>>> sense but it is safe. Lower bound is not so problematic.
>>>>
>>>>
>>>>
>>>>> +       /* create dma mask */
>>>>>
>>>>>> +       mask = ~((1ULL << maskbits) - 1);
>>>>>> +
>>>>>> +       /* get pointer to global configuration */
>>>>>> +       mcfg = rte_eal_get_configuration()->mem_config;
>>>>>> +
>>>>>> +       for (i = 0; i < RTE_MAX_MEMSEG; i++) {
>>>>>> +               if (mcfg->memseg[i].addr == NULL)
>>>>>> +                       break;
>>>>>>
>>>>>
>>> Looking at some other code, it looks like NULL entries might exists. So
>>> should a continue; rather than a break; be used here?
>>>
>>>
>> I do not think so. memsegs are allocated sequentially, so first with addr
>> as NULL implies no more memsegs.
> 
> I was referring to the mem walk functions, rte_memseg_list_walk(). Maybe 
> some having more experience with this area can review/comment.

Pre-18.05, all memsegs are allocated continuously. Memseg lists and 
memseg list walk functions are 18.05+.

Alejandro, perhaps it would be worth it to tag your patchset with 
"pre-18.05" to avoid similar confusion in the future?

-- 
Thanks,
Anatoly