[dpdk-dev] [PATCH v3 07/11] linuxapp/eal: auto detect iova mode

[santosh]

On Thursday 13 July 2017 04:59 PM, Hemant Agrawal wrote:

> On 7/11/2017 11:46 AM, Santosh Shukla wrote:
>> - Moving late bus scanning to up..just after eal_parsing.
>> - Auto detect iova mapping mode, based on the result of
>>   rte_bus_scan_iommu_class.
>>
>> Signed-off-by: Santosh Shukla <santosh.shukla at caviumnetworks.com>
>> Signed-off-by: Jerin Jacob <jerin.jacob at caviumnetworks.com>
>> ---
>>  lib/librte_eal/linuxapp/eal/eal.c | 16 ++++++++++------
>>  1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal.c b/lib/librte_eal/linuxapp/eal/eal.c
>> index 2546b55e4..7b4dd70de 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal.c
>> @@ -799,6 +799,16 @@ rte_eal_init(int argc, char **argv)
>>          return -1;
>>      }
>>
>> +    if (rte_bus_scan()) {
>> +        rte_eal_init_alert("Cannot scan the buses for devices\n");
>> +        rte_errno = ENODEV;
>> +        return -1;
>> +    }
>> +
>
> The original place of the bus scan was with the following factors:
> 1. The bus scan requires the VFIO to be enabled atleast in dpaa2 case.
> (VFIO code still need cleanup to be support non-pci cleanly). I tried moving it before bus_scan, this helped in bus scanning.
>
bus_scan should do scanning, device enumeration, detecting devices and 
interface that device bound to, that interface could be VFIO, UIO, UIO_GENERIC etc..

PCI bus scanning (in eal/) strictly comply to what I mentioned above, thus
aut-detection works gracefully.

However fslmc_bus 'scan' doesn't do device scanning, instead It call vfio dependent
code which ideally should fall in 'resource mapping' category,. ideally should
happen at bus probe time.

Example: 
rte_fslmc_bus_scan()
	--> fslmc_vfio_setup_group
	--> fslmc_vfio_process_group

So it is doing _setup_ inside scan ops, which in PCI(/vfio-pci) case happens 
at probe time (`vfio_setup_device`).

In order to benefit iova auto-detection infrastructure: fslmc bus should
do to two things:

0) fslmc bus scan should look at /sys/bus/platform/drivers/vfio-platform/*
and find out that devices bind to vfio-platform or not, if yes then update kdrv
entry mentioning interface type example VFIO. That-way flsmc bus gets capability to
inform rte_bus about IOMMU capable interface. Right now, existing implementation
don't have means to inform rte_bus about his devices like pci_bus has!.

1) defer the vfio_seup from scan to bus->probe().

 

> 2. During SCAN, the bus may allocate memory to devices or for it's own usages.  rte_malloc or mempool is required in cases to support multi-process environment. (e.g. dpaa2 create dpbp or dpio device memory using the rte_malloc call).
>
If bus scanning adheres to device detection or enumeration then rte_malloc/mempool

not required, Example eal/pci bus scanning.


And in fslmc bus case: if vfio_setup deferred at bus->probe time then
bus->scan won't have memory dependency.

> Since none of the other rte library (mempool, memzone, tailq) is available at this point, it will create significant restriction on the bus scan.
>
> We will prefer if you can re-introduce the "iova_mode" and allow the application choose, which mode it want to run.
>
> This auto-detect logic may not work for many buses and it is going
> to create serious restrictions on the bus_scan code.
>
fslmc is only bus besides PCI. Auto-detection works gracefully for PCI-bus.
Can you give a try to said proposal?

Ideally vfio-platform code should sit into eal/vfio like eal/vfio-pci is.
Otherwise it will keep creating problems for new generic framework like we're
discussing one.

if said proposal doesn't work for you then I will re-introduce iova-mode as
eal arg, that will override iova mapping mode. But IMHO, eal arg should be
intermediate solution. Once vfio-platform code properly re-factored and merged,
We should remove those eal iova-mode args.

>> +    /* autodetect the iova mapping mode (default is iova_pa) */
>> +    if (rte_bus_get_iommu_class() == RTE_IOVA_VA)
>> +        rte_eal_get_configuration()->iova_mode = RTE_IOVA_VA;
>> +
>>      if (internal_config.no_hugetlbfs == 0 &&
>>              internal_config.process_type != RTE_PROC_SECONDARY &&
>>              internal_config.xen_dom0_support == 0 &&
>> @@ -896,12 +906,6 @@ rte_eal_init(int argc, char **argv)
>>          return -1;
>>      }
>>
>> -    if (rte_bus_scan()) {
>> -        rte_eal_init_alert("Cannot scan the buses for devices\n");
>> -        rte_errno = ENODEV;
>> -        return -1;
>> -    }
>> -
>>      RTE_LCORE_FOREACH_SLAVE(i) {
>>
>>          /*
>>
>
>