Date: Mon, 9 Sep 1996 17:23:57 -0600 (MDT) From: "smp@"<csn.net@rick.systemsix.com> To: FreeBSD-gnats-submit@freebsd.org Subject: kern/1592: SMP kernel fix 960909.2 Message-ID: <199609092323.RAA03816@rick.systemsix.com> Resent-Message-ID: <199609092330.QAA28665@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 1592 >Category: kern >Synopsis: kernel incorrectly reads CPU # from APIC ID register >Confidential: no >Severity: serious >Priority: high >Responsible: freebsd-bugs >State: open >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon Sep 9 16:30:01 PDT 1996 >Last-Modified: >Originator: Steve Passe >Organization: New Ideas >Release: FreeBSD 2.2-CURRENT i386 >Environment: smp-sys as of August 27, 1996 Intel XXPRESS motherboard. >Description: The kernel determines the 'number' of the current CPU by reading the 'local APIC ID Register' and masking off the high byte (ie 8 bits) of this 32 bit register. In the 80489 discrete APIC this is an 8-bit field, but in the P5 integrated APIC, it is only a 4-bit field. Although the data book shows the high nibble being zero-ed out on reset, experiments with the Intel XXPRESS motherboard suggests otherwise. There are also other modes where this register becomes a bitfield as oppossed to a discrete number. Since extra bits are sometime set in the high nibble the code fails to detect the proper CPU #. >How-To-Repeat: not relevant. >Fix: 1: in include/apic.h: #define APIC_ID_FIELD 0x0f000000 2: change all places that mask off this field, typically: andl $0xff000000,%e?x to: andl $APIC_ID_FIELD,%e?x these places are: i386/i386/locore.s, line 268 i386/i386/swtch.s, line 452 i386/i386/mplock.s, lines 48, 59, 87, and 99 3: fix cpunumber() in i386/include/smp.h: change line 25: return (apic_base[APIC_ID] >> 24); to: return ((apic_base[APIC_ID] & APIC_ID_FIELD) >> 24); 4: fix macro in i386/include/smpasm.h: change: lines 9-12 #define GETCPUID(reg) \ movl _apic_base, reg; \ movl APIC_ID(reg), reg; \ shrl $24, reg to: #define GETCPUID(reg) \ movl _apic_base, reg; \ movl APIC_ID(reg), reg; \ shrl $24, reg; \ andl $0xf, reg >Audit-Trail: >Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199609092323.RAA03816>