Experimenting with 3.9.3 yielded a find: X86_X2APIC + MAXSMP = serious CPU issues. (Neither of them causes trouble when the other one is missing.) * sluggish kernel boot * a couple times during boot: "BUG: unable to handle kernel" / Oops / kernel panic, NULL pointer dereference, "CPU.*Stuck" * ~twice slower HDD I/O * very high CPU temperature despite no CPU load (reported by physical fan speed and /usr/bin/acpi) * only 1 CPU available in the booted system (should be 2 + 2/HT) * "ACPI Warning.*SystemIO conflicts with Region \GPIO 1" * driver iwlwifi cannot load firmware (could be due to the prolonged boot, but it wasn't *that* long) * "i8042: Can't write CTR while closing KBD port", "i8042: Can't reactivate KBD port" * when running, every now and then the kernel pauses for a fraction of a second This is the first time (vanilla 3.9.3) I tried turning on MAXSMP at all. I suppose testing the combination on an older version is in order. Please, suggest which specific version(s) are interesting in this respect.
Created attachment 102461 [details] .config
Created attachment 102471 [details] cpuinfo
Created attachment 102481 [details] dmesg
Created attachment 102491 [details] dmidecode
Created attachment 102501 [details] kmemleak
Created attachment 102511 [details] lspci -vvv
Created attachment 102521 [details] System.map
Created attachment 102531 [details] vmlinuz SHA256: 647fb1d91aa39900e269a08e46e76f00eba3fecf9c40f5f045f6b30546b97ede
Apologies, the "ACPI Warning.*SystemIO conflicts with Region \GPIO 1" problem is irrelevant to this bug's topic. It's there even without X2APIC and MAXSMP. I suppose the kmemleak contents have nothing to do with this bug as well (just turned on kmemleak for the sake of this bug). If so, please, let me know - I have a graphics-related ugliness to pursue as well (again, not based on X2APIC/MAXSMP).
Downstream bug is at https://bugs.gentoo.org/show_bug.cgi?id=470792