Re: [dpdk-dev] queue to VF assigment in SR-IOV

[Alexander Duyck <alexander.duyck@gmail.com>]

On Mon, Jun 13, 2016 at 4:56 AM, Mauricio Vásquez
<mauricio.vasquezbernal@studenti.polito.it> wrote:
> Hello Alexander,
>
> On Tue, Jun 7, 2016 at 11:31 PM, Alexander Duyck <alexander.duyck@gmail.com>
> wrote:
>>
>> On Tue, Jun 7, 2016 at 1:49 PM, Mauricio Vásquez
>> <mauricio.vasquezbernal@studenti.polito.it> wrote:
>> > Dear All,
>> >
>> > I implemented a program that uses flow director to forward packets to a
>> > specific virtual function, however I faced the problem that I did not
>> > know
>> > which queue belongs to a VF. I found in [1] that in the case of Intel
>> > 82599, queues 0-7 belongs to VF0, 8-15 to VF1 and so on, I tested it but
>> > it
>> > did not work, using the trial and error method I found that queue 0 is
>> > in
>> > VF0, queue 4 in VF1 and so on.
>> >
>> > My question is: is there a standard way to know which queues belong to a
>> > specific VF?
>> >
>> > Thanks in advance
>> >
>> > Mauricio V,
>> >
>> > [1]
>> >
>> > http://www.intel.it/content/dam/www/public/us/en/documents/datasheets/82599-10-gbe-controller-datasheet.pdf,
>> > Table 7-72
>>
>> If you are using the kernel driver the way the queues are laid out
>> depends on the number of VFs allocated and what features are enabled
>> in the kernel.
>
>
> I forgot to mention that I am using the DPDK ixgbe PMD.
>
>>
>> Assuming you are not using DCB you should be able to
>> figure out how many queues are being allocated via VF by looking at
>> the output of "ethtool -l <iface>".  The upper limit on RSS is t he
>> number of queues each pool is allocated.
>>
>> So for example if you only enable up to 31 VFs then the PF driver
>> allocates 4 queues per VF so you would have queues 0 - 3 allocated to
>> VF0, queues 4-7 allocated to VF1, etc all the way through to the PF
>> occupying (num_vfs * 4) to 127.  If you enable 32 or more VFs then the
>> number of queues drops to 2 per VF and RSS on the PF will be limited
>> to the 2 queues following the block reserved for the VFs.
>>
>
> I found that the behavior of the DPDK PMD is almost the same you described:
> 1 - 15 VFs -> 8 queues per VF
> 16 - 31 VFs -> 4 queues per VF
>>= 32 VFs -> 2 queues per VF
>
> But, according to the datasheet it should be
> 16 VFs -> 8 queues per VF
> 32 VFs -> 4 queues per VF
> 64 VFs -> 2 queues per VF
>
> Am I missing something?

The datasheet should be referring to "VM pools".  The PF consumes one
pool for any queues it is using.  As such VFs + 1 is the total number
of pools in use if the PF is active.

> One extra thing that I am not understanding, in the case I assign the
> maximum number of possible VFs, the PF remains without queues?

The device can support at most 64 pools.  So if you are allocating 64
VFs then there are no resources left for the PF to allocate queues
from.

I hope this helps to make it a bit clearer.

- Alex