No PMU support for ACPI-based arm64 systems
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
High
|
dann frazier | ||
Zesty |
Fix Released
|
High
|
dann frazier |
Bug Description
[Impact]
ACPI-based arm64 systems, such as the Qualcomm QDF2400 and the Hisilicon D05, do not currently have PMU support. This means that tools like perf are unable to use the built-in hardware event counters.
[Test Case]
On an ACPI-based arm64 system, run the following commands:
sudo perf list pmu
sudo perf list hw
Without ACPI PMU support, these will be empty.
[Regression Risk]
The changes are restricted to ARM-specific code, other than an added enum value in linux/cpuhotplug.h. This reduces the non-negligible regression risk to the ARM architecture.
For ACPI-based ARM platforms, regression risk is limited because they did not have PMU support previously. However, if this code is buggy, previously working commands that just made use of non-PMU events (e.g. perf top) might start causing problems. To mitigate this, I did a perf_fuzzer run on a QDF2400 (ACPI-based) and confirmed it survived (Note: this included a workaround for LP: #1689855, which will need to be fixed separately once upstreamed).
For non-ACPI-based (i.e. devicetree) ARM platforms, there is a chance that the changes have broken PMU support. To mitigate that, I also did a perf_fuzzer run on a Cavium ThunderX system booted in DT mode, which it survived.
Finally, the non-perf related changes in this series are restricted to a change in arch/arm64/
Changed in linux (Ubuntu): | |
assignee: | nobody → dann frazier (dannf) |
Changed in linux (Ubuntu Zesty): | |
assignee: | nobody → dann frazier (dannf) |
Changed in linux (Ubuntu): | |
status: | New → In Progress |
Changed in linux (Ubuntu Zesty): | |
status: | New → In Progress |
Changed in linux (Ubuntu): | |
importance: | Undecided → High |
Changed in linux (Ubuntu Zesty): | |
importance: | Undecided → High |
description: | updated |
Changed in linux (Ubuntu): | |
status: | In Progress → Fix Committed |
Changed in linux (Ubuntu Zesty): | |
status: | In Progress → Fix Committed |
Changed in linux (Ubuntu Zesty): | |
status: | Fix Committed → Fix Released |
This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification- needed- zesty' to 'verification- done-zesty' . If the problem still exists, change the tag 'verification- needed- zesty' to 'verification- failed- zesty'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.
See https:/ /wiki.ubuntu. com/Testing/ EnableProposed for documentation how to enable and use -proposed. Thank you!