[Bug 1876885] Autopkgtest regression report (linux-oracle-5.4/5.4.0-1019.19~18.04.1)

All autopkgtests for the newly accepted linux-oracle-5.4 (5.4.0-1019.19~18.04.1) for bionic have finished running.
The following regressions have been reported in tests triggered by the package:

zfs-linux/unknown (armhf)


Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-
migration/bionic/update_excuses.html#linux-oracle-5.4

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

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https://bugs.launchpad.net/bugs/1876885

Title:
linux: riscv: set max_pfn to the PFN of the last page

Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Focal:
Fix Released

Bug description:
== SRU Justification Focal/Groovy ==

The current max_pfn equals to zero. In this case, I found it caused users
cannot get some page information through /proc such as kpagecount in v5.6
kernel because of new sanity checks. The following message is displayed by
stress-ng test suite with the command "stress-ng --verbose --physpage 1 -t
1" on HiFive unleashed board.

# stress-ng --verbose --physpage 1 -t 1
stress-ng: debug: [109] 4 processors online, 4 processors configured
stress-ng: info: [109] dispatching hogs: 1 physpage
stress-ng: debug: [109] cache allocate: reducing cache level from L3 (too high) to L0
stress-ng: debug: [109] get_cpu_cache: invalid cache_level: 0
stress-ng: info: [109] cache allocate: using built-in defaults as no suitable cache found
stress-ng: debug: [109] cache allocate: default cache size: 2048K
stress-ng: debug: [109] starting stressors
stress-ng: debug: [109] 1 stressor spawned
stress-ng: debug: [110] stress-ng-physpage: started [110] (instance 0)
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd34de000 in /proc/kpagecount, errno=0 (Success)
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
...
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
stress-ng: debug: [110] stress-ng-physpage: exited [110] (instance 0)
stress-ng: debug: [109] process [110] terminated
stress-ng: info: [109] successful run completed in 1.00s
#

== Fix ==

Upstream commit in linux-next:

commit c749bb2d554825e007cbc43b791f54e124dadfce
Author: Vincent Chen <vincent.chen@sifive.com>
Date: Mon Apr 27 14:59:24 2020 +0800

riscv: set max_pfn to the PFN of the last page

== Test Case ==

Without the patch, running stress-ng --verbose --physpage 1 -t
1 on HiFive unleashed board will trip the bug. With the patch, the test passes as follows:

# stress-ng --verbose --physpage 1 -t 1
stress-ng: debug: [104] 4 processors online, 4 processors configured stress-ng: info: [104] dispatching hogs: 1 physpage
stress-ng: info: [104] cache allocate: using defaults, can't determine cache details from sysfs
stress-ng: debug: [104] cache allocate: default cache size: 2048K
stress-ng: debug: [104] starting stressors
stress-ng: debug: [104] 1 stressor spawned
stress-ng: debug: [105] stress-ng-physpage: started [105] (instance 0) stress-ng: debug: [105] stress-ng-physpage: exited [105] (instance 0) stress-ng: debug: [104] process [105] terminated
stress-ng: info: [104] successful run completed in 1.01s


== Regression Potential ==

Small, this correctly fixes the max_pfn and max_low_pfn to the correct
end of DRAM location. The fix now can be shown to set these
appropriately because stress-ng no longer triggers this corner case.

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