** Changed in: linux (Ubuntu Focal)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1882088
Title:
[UBUNTU 20.04] smc: SMC connections hang with later-level
implementations
Status in Ubuntu on IBM z Systems:
In Progress
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Focal:
Fix Committed
Status in linux source package in Groovy:
In Progress
Bug description:
SRU Justification:
==================
[Impact]
* Connections from later-level SMC (protocol) versions to an SMC-
enabled server on Linux hang.
* Later-level versions of SMC (although backwards-compatible) present
a higher version number and use larger messages during the CLC
handshake.
* The solution to avoid such hangs is to introduce toleration for
later version numbers, and support CLC messages of arbitrary length.
[Fix]
* fb4f79264c0fc6fd5a68ffe3e31bfff97311e1f1 fb4f79264c0f "net/smc:
tolerate future SMCD versions"
[Test Case]
* Requires two IBM z13/z13s GA2 or LinuxONE Rockhopper/Emperor systems
with RoCE Express adapter v2(.1) for SMC-D usage.
* One system needs to run the initial SMC-D version, the other a newer
version.
* Establish a connection between both system and monitor/verify if
it's reliable or if it hangs.
[Regression Potential]
* The regression can be considered as medium to low:
* Since SMC-D is a pretty special way of doing shared memory
communications and not that wide-spread.
* However, the code that is changed is common code.
* But the patch is straight forward and only modifies
/net/smc/smc_clc.c and /net/smc/smc_clc.h
* It largely bumps limits (allows larger messages), adds a check and
introduces toleration, rather than changing control or flow.
[Other]
* The above fix is currently in 'linux-next' and tagged with
next-20200709.
* It is still assumed that it gets accepted for 5.8.
* However, since this is not guaranteed this SRU request is for focal
and groovy - to make sure that no potential regressions are introduced
in case the patch will not end up in 5.8.
__________
Description: smc: SMC connections hang with later-level implementations
Symptom: Connections from later-level SMC versions to an SMC-enabled
server on Linux hang.
Problem: Later-level versions of SMC present, although backwards-
compatible, a higher version number, and use larger messages
during the CLC handshake.
Solution: Adjust for tolerating later version numbers, and support CLC
messages of arbitrary length.
Reproduction: Enable a server on Linux for SMC, and connect using a later-
level version of SMC
Applicable for: Ubuntu 20.04
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