Bug 1974103

Summary: Over 300 lines "rngd[926]: Entropy Generation is slow, consider tuning/adding sources" generated during aws arm instance boot
Product: Red Hat Enterprise Linux 8 Reporter: Frank Liang <xiliang>
Component: rng-toolsAssignee: Vladis Dronov <vdronov>
Status: CLOSED WONTFIX QA Contact: Vilém Maršík <vmarsik>
Severity: medium Docs Contact:
Priority: medium    
Version: 8.5CC: core-kernel-mgr, leiwang, linl, ribarry, rvr, skozina, vkuznets, ymao
Target Milestone: betaKeywords: Rebase, Triaged
Target Release: ---   
Hardware: aarch64   
OS: Linux   
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Last Closed: 2021-08-23 16:15:17 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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t4g.large_journal_20210620.log none

Description Frank Liang 2021-06-20 14:40:32 UTC
Created attachment 1792527 [details]
t4g.large_journal_20210620.log

Description of problem:
In aws, boot a RHEL-8.5(RHEL-8.5.0-20210619.n.0) arm instances, there are over 300 lines of the same log produced in the journal log.
# journalctl |grep -i 'Entropy Generation is slow,'|wc -l
312
# systemctl status rngd
● rngd.service - Hardware RNG Entropy Gatherer Daemon
   Loaded: loaded (/usr/lib/systemd/system/rngd.service; enabled; vendor preset: enabled)
   Active: active (running) since Sun 2021-06-20 13:46:46 UTC; 11min ago
 Main PID: 926 (rngd)
    Tasks: 3 (limit: 11944)
   Memory: 7.3M
   CGroup: /system.slice/rngd.service
           └─926 /usr/sbin/rngd -f --fill-watermark=0

Jun 20 13:46:48 ip-10-22-1-148.us-west-2.compute.internal rngd[926]: Entropy Generation is slow, consider tuning/adding sources
Jun 20 13:46:48 ip-10-22-1-148.us-west-2.compute.internal rngd[926]: Entropy Generation is slow, consider tuning/adding sources
Jun 20 13:46:48 ip-10-22-1-148.us-west-2.compute.internal rngd[926]: Entropy Generation is slow, consider tuning/adding sources
[root@ip-10-116-2-114 ec2-user]# rpm -q rng-tools
rng-tools-6.8-5.el8.aarch64


Version-Release number of selected components (if applicable):

RHEL Version:
RHEL-8.5(4.18.0-314.el8.aarch64)

How reproducible:
100%

Steps to Reproduce:
1. start a RHEL-8.5 arm instance, eg.  t4g.large
2. Check journal log after boot.

Actual results:
Too many same log fill the journal log

Expected results:
1 or 2 lines are sufficient.

Additional info:
N/A

Comment 2 Vladis Dronov 2021-08-08 10:11:48 UTC
an update for the rng-tools is being added to RHEL8: rng-tools-6.13-1.git.d207e0b6.el8.
one of the features is a support for ARM v8.5 RNDR Instruction RNG (rndr).
with RNDR rng-tools should have enough entropy, you can test the candidate package at:

https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=38749313

i've double-checked that RNDR code is really built, unfortunately, a test ARM machine
itself does not support RNDR:

# uname -a
Linux apm-mustang-b0-11.khw4.lab.eng.bos.redhat.com 4.18.0-305.el8.aarch64 #1 SMP aarch64 aarch64 aarch64 GNU/Linux

# /usr/sbin/rngd -f -d -x jitter -n rndr
Disabling 6: JITTER Entropy generator (jitter)
Enabling 4: ARM v8.5 RNDR Instruction RNG (rndr)
Initializing available sources
[hwrng ]: Initialized
[rndr  ]: No HW SUPPORT
[rndr  ]: Initialization Failed
Kernel entropy pool size 4096, pool watermark 3072