[22.10 FEAT] Enablement for MIO Instructions - rdma-core part

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Enablement for MIO Instructions - rdma-core part

Feature Description

Make use of the new PCI Load/Store instructions in the rdma-core package.

The existing support for rdma-core uses the privileged functions for RDMA traffic, which rely on add'l syscalls. Though syscalls on s390 are said to be not as expensive as on other platforms, it still defeats the purpose of the userspace RDMA approach, and the context switches still cost us.
Furthermore, the new instructions operate on virtual addresses instead of function handles, with Millicode handling the address translation. This is more similar to real MMIO, and allows for real re-mapping..

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------- Comment From <email address hidden> 2022-01-30 22:11 EDT-------
This also has a kernel part:
Canonical LP#1959543 - IBM BZ#196211 [22.04 FEAT] Enablement for MIO Instructions - kernel part

[Frank Heimes (fheimes)]

Please share the rdma-core version that incl. this 'enablement for MIO instructions for s390x' and/or the needed commit IDs - updating ticket to Incomplete for now...

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------- Comment From <email address hidden> 2022-02-28 10:33 EDT-------
The code for this feature has just been merged into rdma-core upstream a few minutes ago: https://github.com/linux-rdma/rdma-core/pull/1122

I would thus expect it to be included in versions >v39.0

[Frank Heimes (fheimes)]

Unfortunately we are now past feature freeze, which was last Thu the 24th of February.
Version 39.0-1 landed in jammy (22.04).
Since this is about z15 hw exploitation, I /think/ there is a little chance to SRU this later.
But this needs now further investigation and discussions ...

[Frank Heimes (fheimes)]

@Niklas btw. do you have an indication when a new version > v39.0 might arrive?

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------- Comment From <email address hidden> 2022-03-15 06:29 EDT-------
This item did not make it in time for jammy, therefore moving to Ubuntu 22.10.
Updating target milestone from 22.04 ==> 22.10

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------- Comment From <email address hidden> 2022-04-11 07:31 EDT-------
(In reply to comment #12)
> This item did not make it in time for jammy, therefore moving to Ubuntu
> 22.10.
> Updating target milestone from 22.04 ==> 22.10

This feature made it into upstream rdma-core v40. Is there information already if this will be available in 22.10?
(https://github.com/linux-rdma/rdma-core/releases/tag/v40.0)

[Benjamin Drung (bdrung)]

I will update rdma-core to v40 in Debian soonish. Then this version can by synced. Expect this version in 22.10 quite early in the release cycle.

[Frank Heimes (fheimes)]

That's great - thx Benjamin!

[Benjamin Drung (bdrung)]

Uploaded rdma-core 40.0-1 and synced to Ubuntu. It's in kinetic-proposed now.

[Frank Heimes (fheimes)]

Fantastic, thx Benjamin!
(Updating status to Fix Committed.)

[Frank Heimes (fheimes)]

Meanwhile rdma-core 40.0-1 left proposed and landed.
Updating this LP bug to Fix Released and closing it.