[Ubuntu 18.04] Error parsing PCC subspaces from PPCT" is splashed to screen

[Sujith Pandel]

When installing and booting to Ubuntu 18.04 Server, we see this error being shown on screen (Attached Screenshot)

Setup details- Take a DellEMC 14G server and start installation of Ubuntu 18.04 Server. Observe this message in #dmesg.

Cosmetic error message, no functionality loss.

Upstream patch details:
https://www.spinics.net/lists/linux-acpi/msg81863.html
Please include these in future builds of Ubuntu 18.04.

Uploading the #dmesg logs.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1779605

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Sujith Pandel (sujithpandel)]

Moving back to 'Confirmed' as mentioned in c#3, since dmesg logs are already attached.
If more logs are required, please let me know.

[Joseph Salisbury (jsalisbury)]

There are three patches in the following patch set:
https://www.spinics.net/lists/linux-acpi/msg81863.html

Are all three patches needed, or just a subset?

Also, it looks like the patch set is now on v3. Since this patch set has not landed in mainline yet, do you think there will be additional revisions?

[Sujith Pandel (sujithpandel)]

The v4 was proposed and applied:
https://patchwork.kernel.org/patch/10404957/

I feel only the 3/3 (3rd patch in whole series) is enough to deal with this bug.
If you could give me a test kernel, I shall verify it and confirm it here.

[Joseph Salisbury (jsalisbury)]

I built a test kernel the with v4 3/3 patch. The test kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1779605

Can you test this kernel and see if it resolves this bug?

Note about installing test kernels:
• If the test kernel is prior to 4.15(Bionic) you need to install the linux-image and linux-image-extra .deb packages.
• If the test kernel is 4.15(Bionic) or newer, you need to install the linux-modules, linux-modules-extra and linux-image-unsigned .deb packages.

Thanks in advance!

[Sujith Pandel (sujithpandel)]

Verified the test-kernel shared in the above link on the same setup where the issue was seen with bionic kernels.

Uploading dmesg.

Issue seems to be fixed and change observed now is:

[ 0.229581] Detected 1 PCC Subspaces
[ 0.229581] Registering PCC driver as Mailbox controller

[Joseph Salisbury (jsalisbury)]

Mainline commit 8f8027c5f935 is now in the Bionic master-next repo:
41b696d80377 mailbox: PCC: erroneous error message when parsing ACPI PCCT