From owner-freebsd-current Wed Jul 17 14:16:46 2002 Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C8D3237B409 for ; Wed, 17 Jul 2002 14:16:40 -0700 (PDT) Received: from tonnant.cnchost.com (tonnant.concentric.net [207.155.248.72]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5ACA943E31 for ; Wed, 17 Jul 2002 14:16:30 -0700 (PDT) (envelope-from bakul@bitblocks.com) Received: from bitblocks.com (adsl-209-204-185-216.sonic.net [209.204.185.216]) by tonnant.cnchost.com id RAA10793; Wed, 17 Jul 2002 17:16:02 -0400 (EDT) [ConcentricHost SMTP Relay 1.14] Message-ID: <200207172116.RAA10793@tonnant.cnchost.com> To: Terry Lambert Cc: Szilveszter Adam , Peter Wemm , freebsd-current@FreeBSD.ORG Subject: Re: Interesting panic very early in the boot In-reply-to: Your message of "Wed, 17 Jul 2002 11:19:31 PDT." <3D35B533.9DF22814@mindspring.com> Date: Wed, 17 Jul 2002 14:16:00 -0700 From: Bakul Shah Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > That there could be a real error in that code surprises me, since > Peter really knows what he's doing, even if that low in the > hardware, there are undocumented interactions that even Intel's > errata doesn't seem to know about. Turns out the workaround is to use DISABLE_PG_G. Two things made me try this. One: In his commit of pmap.c and locore.s on 7/12 7:56 Peter had this to say: +-- |- Try and fix some very bogus PG_G and PG_PS interactions that were bad | enough to cause vm86 bios calls to break. vm86 depended on our existing ... |New option: DISABLE_PG_G - In case I missed something. +-- Two: cvs diff -r1.336 -r1.337 of i386/pmap.c showes that #ifdef SMP was changed to ifndef DISABLE_PG_G and it is in here that pfeflag is set (pfeflag is what guards the code at the crash site!). > set boot_ddb Didn't do this. > set boot_gdb Did this. I though the above two were mutually exclusive options. boot_ddb should be renamed to start_in_debugger or something. Though boot -d is what I was really looking for. > higher/later code, the root cause is catually in locore.s. Happy > bug hunt! ;^). Thanks but looks like I easily escaped from the hunt this time :-) -- bakul To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message