I have used Linux on my PC for a long time. Some time recently, there is a new kernel error message on the text console.
It also appears as a message in red in journalctl -p err. It did not appear like this before.
Question: Why did this change?
Notice: I am writing this very general question, in order to host the answer below.
Notice: ACPI error messages on specific systems might have more specific causes, problems, and solutions. For example, see these two questions:
My error messages are:
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT0._GTF] (Node ffff8d859a5caaa0), AE_NOT_FOUND (20160831/psparse-543)
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT0._GTF] (Node ffff8d859a5caaa0), AE_NOT_FOUND (20160831/psparse-543)
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT4._GTF] (Node ffff8d859a5ca758), AE_NOT_FOUND (20160831/psparse-543)
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT5._GTF] (Node ffff8d859a5ca9b0), AE_NOT_FOUND (20160831/psparse-543)
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT4._GTF] (Node ffff8d859a5ca758), AE_NOT_FOUND (20160831/psparse-543)
ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
ACPI Error: Method parse/execution failed [\_SB.PCI0.SAT0.SPT5._GTF] (Node ffff8d859a5ca9b0), AE_NOT_FOUND (20160831/psparse-543)