Jan Kiszka <jan.kiszka@xxxxxxxxxxx> writes: > Am 2015-04-29 um 18:47 schrieb Bandan Das: >> >> Why do we allow writes to APIC_ID ? On all _newer_ processors, it's >> read only. The spec doesn't explicitly mention it though, or atleast >> I couldn't find it. Does userspace have a reason to modify it ? > > The APIC ID is read-only for x2APIC. It remains R/W for xAPIC. Are you sure ? In 10.4 of the SDM, there is Note that says "In processors based on Intel microarchitecture code name Nehalem the Local APIC ID Register is no longer Read/Write; it is Read Only." And I can verify on a SandyBridge and Haswell system that it's RO there too. In fact, that was one of the reasons I had submitted a patch to remove verify_local_APIC() from x86/kernel/apic.c (4399c03c678) If I am wrong we need to revert atleast the associated commit message :) > Jan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
