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

[Alexander Duyck]

On Tue, Jun 7, 2016 at 1:49 PM, Mauricio Vásquez
<mauricio.vasquezbernal at 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.  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.

There are a few other configurations such as if DCB is enabled I
believe it is possible to get 8 queues per VF if less than 16 VFs are
allocated but in such a case you would not have access to RSS.  In
this case if the maximum combined queue count reported is 1 you would
need to check to see how many TCs are being supported by the PF in
order to determine if the queue count is 4 or 8 per VF.

- Alex