In the Linux kernel, the following vulnerability has been resolved:

coresight: ete: Always save state on power down

System register ETMs and ETE are unlikely to be preserved on CPU power down. The ETE DT binding also never documented "arm,coresight-loses-context-with-cpu" so nobody would have legitimately been able to use that binding to fix it and ACPI has no such binding at all.

Fix it by hard coding the setting for sysreg ETMs (ETE is always sysreg) or ACPI boots. Use a local variable when setting up save state so that it's immune to concurrent probing when devices have different configurations which is an issue with modifying the global.

This fixes the following error when using Coresight with ACPI on the FVP which supports CPU PM:

coresight ete0: External agent took claim tag WARNING: drivers/hwtracing/coresight/coresight-core.c:248 at coresight disclaim device unlocked+0xe0/0xe8, CPU#0: perf/117