Re: RSS Hash value returned by the gvnic pmd dpdk driver not matching Toeplitz

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 5/15/2024 9:20 AM, Nagesh Mallappa wrote:
> Hi Team,
> 
> We are using a C3 GCP instance having GVNIC with DPDK enabled.
> We are using latest version of DPDK ( dpdk-24.03 ) to configure RSS key,
> we understand C3 GCP instance with gvnic supports Toeplitz rss algorithm
> ( Reference
> - https://github.com/google/compute-virtual-ethernet-dpdk/blob/main/gve_ethdev.c <https://github.com/google/compute-virtual-ethernet-dpdk/blob/main/gve_ethdev.c> ), but we are hitting below issue.
> 
> *Problem Statement - The RSS Hash value returned by the gvnic driver is
> different and is not matching the one computed by Toeplitz.*
> 
> Using below script to compute rss hash value from Toeplitz.
> (https://gist.github.com/joongh/16867705b03b49e393cbf91da3cb42a7
> <https://gist.github.com/joongh/16867705b03b49e393cbf91da3cb42a7>)
> 
> Consider below data to compute RSS Hash value -
> 
> Source IP - 79.124.62.122
> Destination IP - 192.168.7.28
> Source Port - 49442
> Destination Port - 55327
> RSS Key - {0x94e3e97e, 0x4abac401, 0x1e0edbf, 0xe059e1f4, 0xb6e27dff,
> 0xdf55c916, 0xe9e6e4db, 0x1f9fb82c, 0x1e0edbf, 0xe059e1f4}
> 
> *Hash Value returned by Toeplitz - 0x8bbafd0f*
> 
> Gvnic dpdk pmd driver which uses Toeplitz RSS hash algorithm too is
> expected to compute above RSS Hash value but we see the Hash value
> stored in dpdk mbuf to be 0xc6a15941 which is not right.
> From the DPDK side we have ensured RSS offloading configuration is done
> appropriately, but still we are seeing above mismatch.
> 
> We request you to please help us understand why this mismatch is
> happening and is this expected behavior of gvnic on C3 instance.
> 
> 

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