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

Eelco Chaudron echaudro at redhat.com
Tue Jul 10 13:55:40 CEST 2018



On 10 Jul 2018, at 13:43, Alejandro Lucero wrote:

> On Tue, Jul 10, 2018 at 12:33 PM, Burakov, Anatoly <
> anatoly.burakov at intel.com> wrote:
>
>> 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?
>>
>>
> Yes, that will help. I'm sending a new version shortly and I'll make 
> it
> clear.

Thanks, I’ll review the new version if it’s ready before the end of 
tomorrow CET, as I will be on PTO.




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