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

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

[Nagesh Mallappa]

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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
),
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)

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.

Thanks,

Nagesh

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

[Stephen Hemminger]

On Wed, 15 May 2024 13:50:38 +0530
Nagesh Mallappa <mallappanagesh@gmail.com> 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
> ),
> 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)
> 
> 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.

Could you see if it is a driver byte order issue by byteswapping the key?

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

[Nagesh Mallappa]

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Hi Stephen,

Thanks for your response,
I have verified that too, but that is not the case.

Thanks,
Nagesh

On Wed, May 15, 2024 at 8:34 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Wed, 15 May 2024 13:50:38 +0530
> Nagesh Mallappa <mallappanagesh@gmail.com> 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
> > ),
> > 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)
> >
> > 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.
>
> Could you see if it is a driver byte order issue by byteswapping the key?
>

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

[Stephen Hemminger]

On Wed, 15 May 2024 21:19:15 +0530
Nagesh Mallappa <mallappanagesh@gmail.com> wrote:

> Hi Stephen,
> 
> Thanks for your response,
> I have verified that too, but that is not the case.

Does it work the same with Linux native kernel driver.
If so, then comparing the code there might give some insight.

PS: I don't use or any connection with Google, just trying to
give insight based on other previous drivers with similar bugs.

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

[Nagesh Mallappa]

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Hi Stephen,

Yes we have tried on Freebsd driver, we are hitting RCC hash issues here
too.
The Issue seems to be with the backend Gvnic on C3 GCP Instance.
Trying to get help from the DPDK community if there is any workaround or
fix for the RSS Issue on GVNIC DPDK PMD for C3 GCP Instance.

Thanks,
Nagesh

On Thu, May 16, 2024 at 4:27 AM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Wed, 15 May 2024 21:19:15 +0530
> Nagesh Mallappa <mallappanagesh@gmail.com> wrote:
>
> > Hi Stephen,
> >
> > Thanks for your response,
> > I have verified that too, but that is not the case.
>
> Does it work the same with Linux native kernel driver.
> If so, then comparing the code there might give some insight.
>
> PS: I don't use or any connection with Google, just trying to
> give insight based on other previous drivers with similar bugs.
>

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

[Ferruh Yigit]

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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