From owner-freebsd-ppc@freebsd.org Mon Sep 12 21:01:20 2016 Return-Path: Delivered-To: freebsd-ppc@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1888CBD8E2E for ; Mon, 12 Sep 2016 21:01:20 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 073DA6E9 for ; Mon, 12 Sep 2016 21:01:20 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id u8CL1IfF024980 for ; Mon, 12 Sep 2016 21:01:19 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-ppc@FreeBSD.org Subject: [Bug 205458] 11.0-CURRENT/10-STABLE powerpc64: a PowerMac G5 specific sys/powerpc/ofw/ofw_machdep.c change for reliable PowerMac G5 booting (with lots of RAM) Date: Mon, 12 Sep 2016 21:01:18 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: patch X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: nwhitehorn@FreeBSD.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Sep 2016 21:01:20 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D205458 Nathan Whitehorn changed: What |Removed |Added ---------------------------------------------------------------------------- Status|New |In Progress CC| |nwhitehorn@FreeBSD.org --- Comment #4 from Nathan Whitehorn --- I've finally understood why this patch does anything useful. Open Firmware = runs in virtual mode on the Powermac G5. This runs inside the kernel page table, which preserves all address translations made by OF before the kernel start= s; as a result, the kernel address space is a strict superset of OF's. Where this explodes is if OF uses an unmapped SLB entry. The SLB fault hand= ler runs in real mode and refers to the PCPU pointer in SPRG0, which blows up t= he kernel. Having a value of SPRG0 that works for the kernel is less fatal than preserving OF's value in this case. I believe that OF's SPRG0 is maintained only for compatibility with some G4 Apple hardware, the eMac in particular, but will check and we can move on w= ith this. I think it should be safe to wrap this in an #ifdef __powerpc64__. --=20 You are receiving this mail because: You are on the CC list for the bug.=